A Vegetarian Dinner (Recipe: Leek & Mushroom Bake with Polenta Crust)

We tend to eat at least seventy-five percent vegetarian during the week, yet for some reason when I entertain on the weekends, I often feel obligated to serve up a big slab of meat. It might be a roast chicken, filet of salmon, or lamb curry, but seldom is it vegetarian fare.

As I was assembling this mushroom and polenta gratin, I wondered to myself why I always chose a protein as my main dish and why didn’t I indulge my friends in some of the healthier and more adventurous dishes that we eat day to day?

Whatever the reason – expectations, tastes or tradition – it became apparent as I dished up this gratin around our dinner table that I had created something well-worth sharing. Meat-lovers, or no meat-lovers.

This leek and mushroom bake with its polenta-Parmesan crust more than holds its own as a main dish – it steals the show. Aromatic leeks and no-nonsense celery are paired with woodsy, garlic-sauteed mushrooms to form the base of the bake. They are topped with a smooth Bechamel (a basic white sauce) that has been jazzed up by a handful of sharp Parmesan. The final layer is thin cakes of cooked and cooled polenta and everything is topped with more cheese.

As our creation bakes, the mushrooms and leeks perfume the dish and the polenta bubbles into a lovely crust. It is then ready to be spooned up alongside more seasonal vegetables for a perfect autumn meal.

Do-Ahead Tips and Ingredient Sourcing

Most vegetarian dinners come together so simply that it would be easy to glance over this recipe and think “Now why would I ever bother with four steps?” but this recipe is special. I think even holiday dinner special – especially if you’re hosting a few friends and family who skip the Christmas ham and Thanksgiving turkey.

Another reason why I’m sharing this dish is because it can easily be broken down into manageable steps that can all be completed one or two days in advance. In fact, once the whole shebang is assembled, it can hold for 24 hours, refrigerated and sealed in plastic wrap, until it is ready to be baked off and served piping hot.

Do ahead? Check.

Step-by-step? Yes, indeed.

So what about those funky ingredients, then? Well, if you are accustomed to preparing vegetarian main meals, you probably are already familiar with dried mushrooms and polenta, not to mention whole leeks. But in case those sound a little frightening, here’s a quick schooling.

Polenta ~ You’ve probably spotted beautiful bright yellow polenta in the bulk food section of your organic store already. It might even be labeled as cornmeal, as it is essentially the same thing. For our breakfasts, I buy the quick cooking cornmeal, but for this recipe (and if you’re ever cooking and cooling polenta to grill) select the coarse polenta.

Dried Mushrooms ~ Chosen for this dish because of their high concentration of flavor, dried mushrooms play the star role of the gratin and provide a ‘meatiness’ that gives the dish a well-rounded, nourishing feel. Fresh mushrooms just wouldn’t provide the same texture, plus I’m always looking for ways to use up the dried wild mushrooms that my mother sends me.

Look for dried mushrooms such as shiitake, morels, and porcini at your health food store or farmer’s market. You can also find them for purchase online.

Leeks ~ One of my favorite winter vegetables is the humble leek. I featured it last year as a Spotlight Ingredient, where you can read all about buying, storing and cleaning the leek.  The subtle flavor of the leek lends itself to a beautiful pairing with the mushrooms in this bake and shouldn’t be replaced with onion. So go ahead and buy and bundle. You can always make this or this soup with the remaining stalks.

Parmesan ~ I always have a chunk of this firm Italian cheese in my refrigerator – and the real stuff, too. It is expensive, but a little goes a very long way in the flavor department. You could also substitute Pecorino Romano in this dish, or, in a pinch, sharp cheddar. You can find Parmesan at almost any grocery store, although I go out of my way to purchase it from an Italian grocer because it costs much less.

Recipe: Leek & Mushroom Bake with Polenta-Parmesan Crust

Serves 6 as a main dish, 8-10 as a side dish.


  • 3 ribs celery
  • 2 leeks, white part only
  • 1 Tablespoon olive oil
  • 1 Tablespoon butter
  • 2 cloves garlic, peeled
  • 2 cups dried mushrooms (I used shiitake and morels)
  • 1 recipe polenta crust
  • 1 recipe Bechamel sauce
  • 1/2 cup grated Parmesan cheese


Step 1: Polenta Crust

  • 1 1/2 cups coarse polenta
  • 6 cups water
  • 1 teaspoon salt
  • 2 tablespoons butter
  1. Bring water and salt to a boil in a heavy bottomed sauce pot. Over medium heat, whisk polenta into boiling water, a handful at a time, until it is all incorporated.
  2. Reduce heat to medium-low and cook polenta, stirring frequently, for about 30 minutes. It will become quite thick. Tip: While your polenta is cooking, prepare steps 2 and 3 of this recipe.
  3. Remove polenta from heat and beat in butter. Pour onto a buttered baking sheet and spread out with a spatula into a rough 9×13 rectangle. Polenta will be moldable.
  4. Cover with plastic wrap and refrigerate until firm or up to two days.

Step 2: Roasted Vegetables & Sauteed Mushrooms

  1. Preheat oven to 400°F and lightly oil a baking sheet or roasting pan.
  2. Wash and dry celery and leeks. Slice leeks into 1/4 inch ‘coins’. Chop celery ribs into 1/4 inch pieces also.
  3. Place vegetables in a single layer on the baking sheet and roast in the oven for 15 minutes. Give the pan a shake and rotate it at least once during the cooking process.
  4. Soak mushrooms in warm water for 20 minutes (Tip: you can make your Bechamel sauce during this time).
  5. Melt 1 tablespoon butter in a medium sauce pan. Bang garlic cloves with the flat side of a knife to bruise them and toss them into the butter.
  6. Drain mushrooms, squeezing out as much liquid as possible, and add them to the garlic butter.
  7. Season mushrooms with salt and pepper and cook over medium heat for about 7 minutes.

Step 3: Basic Bechamel Sauce

  • 3 Tablespoons butter
  • 1/3 cup all-purpose flour
  • 2 1/4 cups milk
  • 1/2 teaspoon salt
  1. Melt butter in a medium pan or sauce pot over medium heat. Dump the flour in all at once and whisk to combine. Cook, stirring constantly, for about two minutes to develop a little more flavor and avoid a ‘floury’ taste in your bechamel.
  2. Gradually add in the milk, whisking vigorously to emulsify sauce and eliminate lumps. Once all the milk has been added, bring to a slow boil and stir until thick and smooth.
  3. Season with salt to taste and reserve until ready to use.

Step 4: Assembly and Baking

  1. Preheat over to 350°F and butter a 9×13 baking dish.
  2. Combine roasted celery and leeks in the dish and spread out to cover the bottom in a single layer. Top with the sauteed mushrooms, uniformly scattered throughout.
  3. Pour bechamel sauce over the vegetables and distribute evenly using a rubber spatula. Sprinkle with 1/4 cup grated Parmesan cheese.
  4. Cut chilled polenta into rectangles and arrange on top of the bechamel. Sprinkle with remaining 1/4 cup of Parmesan cheese.
  5. Place dish in oven and bake, uncovered, for about 40 minutes, until top is browned and the bechamel is bubbling up the sides.

Serve at once.

What is your favorite vegetarian main dish?

About Aimee

Cooking has always been Aimée's preferred recreational activity, creative outlet, and source of relaxation. After nearly ten years in the professional cooking industry, she went from restaurant to RSS by trading her tongs and clogs for cookie cutters and a laptop, serving as editor here at Simple Bites. Her first book, Brown Eggs and Jam Jars - Family Recipes from the Kitchen of Simple Bites, was published in February 2015.

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  1. I would love to try this Leek & Mushroom Bake with Polenta-Parmesan Crust… Looks yummy, and I always love mushroom! Thank you for sharing this recipe.

  2. This looks so yummy! I am with you on the serving meat. I tend to make pot roast, or some type of meat main dish that is “classic american” when we have guests…not entirely sure why. I think that because my family has such different tastes than main stream, I don’t want to turn everyone off from visiting us 🙂

  3. I don’t think I have a favorite vegetarian dish. I often end up (when cooking for only me) eating vegetarian because I know if I cook up a bunch of meat, I won’t end up eating it (weird, I know) and wasting it. This dish sounds yummy, but as it’s full of mushrooms, I know the other person in my house won’t eat it. Maybe I’ll make a half version for me. Any idea if this can be frozen and reheated?

  4. what a perfect fall dinner. this looks so cozy and delicious!

  5. This looks like it needs to be in my weekly dinner rotation. Looks perfect for Sunday supper 🙂 Thanks for sharing!

  6. Christen Babb says

    Morel mushrooms make this extra special…they are my absolute favorite! I can’t WAIT to try this one!

    We usually do only one or two meat dishes a week and the rest vegetarian. I try to make one large portion of meat a week, so I can re-purpose the leftovers into something like a casserole, or a hearty soup, bulking it up with vegetables, grains and good ol’ beef or chicken stock. If I’m lucky, I can make two portions of soup or casserole from the leftover meat – one to eat and one to freeze. Stretching three meals out of one large piece of meat can save tons of time and money!

    • Christen, my mothers sends me dried wild morels that she picks herself. They are one of the most precious items in my kitchen and SO good!

  7. Oh lord, Aimée, you’ve got so many of my favorite ingredients in one killer casserole. I could probably live on this for a month.

    • Hah! We reheated it three times and yuuuummm. I only wish I could have enjoyed it with a crisp white wine. =) I’ll have to make it again when the baby comes.

      Gratin + Green Salad + Wine = The perfect meal.

  8. It is too funny that you posted this recipe today. Yesterday I sent my husband to the store for 1.5 lbs of fresh wild mushrooms. He came home with 1 lb of fresh and another 0.5 lbs of dry. I can’t believe he spent SO MUCH on mushrooms. So now I have 8 little boxes of dried mushrooms that need to be cooked at some point!

  9. Mushrooms are my favourite vegetable! I could eat this today, it looks so creamy and comforting.

  10. I am always looking for new vegetarian dishes to try. We have been eating less and less meat, but I need something to replace those meals. This looks like an awesome choice!

  11. I would love this if your were to make it for me. I know what you mean though, I’m leaning towards tradition. I can remember by Granny doing the same thing. Meals of vegetables during the week, meat on the weekends. I seem to have followed in her footsteps. Your dish and post have me rethinking that concept.

    • I think we all need to rethink the concept. We rave about meatless meals, but they are never our ‘fallback’ plan for company.

      Thanks for stopping by!

  12. Rebecca ~ Sweet Baby Yams says

    This looks delicious! I’ve been trying to find recipes containing polenta so this is perfect. Thanks!

  13. Aimee, this bake looks ah-mazing! We want to get in on the meatless Monday game and this will be perfect for it! Looks delicious and the pictures are beautiful!

  14. Would you have any substitution suggestions for a household in which celery is not permitted? (Garcia effect… illogical, but very real.) Thanks!

  15. This looks wonderful, Aimee! Something I would have never thought to put together but that I absolutely have to try now. Yum!

  16. looks fabulous! I have dried shiitakes (from the Asian market), but not morels. We also eat vegetarian the way you described. THere’s something lovely about a roast beef for Sunday dinner! But if we have a lot of rich meals out, I make simpler vegetarian meals to balance it out.

    One of our favorite vegetarian meals is rice and dhal, with maybe a chutney or greens on the side. It freezes so well that I always make a double batch.

  17. This looks wonderful! I love leeks and am always trying to find more recipes. Pinning this to try later! Our favorite vegetarian dish is a roasted eggplant & zucchini lasagna! 🙂

  18. That looks absolutely delicious! I’m going to have to try this out, now I need to get my hands on some dried mushrooms I can actually afford!

  19. I was so excited to try this as I’m always trying to look for interesting vegetarian dinners that are “company” worthy. I ended up making it for a girls night with my mom who has severe IBS that has her on a primarily vegan diet, though she can process sheep and goat’s milk cheeses. So handy substitutions to the rescue! Subbed Pecorino Romano, a hard sheep’s milk cheese for the Parmesan, which was great. The Bechamel was a little tougher, but I used a 1 1/2 cups of coconut milk, and 3/4 cup of the water I reserved when draining the mushrooms. The mushroom water helped cut the sweetness and thickness of the coconut milk. Turned out great and got rave reviews. Thanks for a great recipe!

  20. This was delicious, and I must admit, even better on the second day for leftovers! I made the sauce with half soy milk and have 2% milk and it worked really well. Also, I didn’t have parmesan so I used a sharp cheddar blend. Loved it but will definitely get the good stuff for next time. My only advice for others cooking this dish is to make sure the polenta solidifies for a good while before layering and baking. We only had it in the fridge for an hour, which didn’t seem to be long enough (it was a bit mushy the first time we ate it). After the final dish sat in the fridge all night, it was perfect.

  21. Looks so fantastic!! I will make this (vegan and gluten free version) for the rest of the family that eats cooked foods. I bet it smells divine. Thanks so much for sharing.
    Peace and Raw Health,

  22. This dish looks scrumptious. Can anyone tell me if this recipe freezes well? As I am a one person household, any meals I prepare must either be easy to reduce recipe size to 1/2, 1/4, etc, or freeze leftovers to eat at a later date.

  23. Jim Hewitt says

    why don’t you provide option to print your great recipes?
    Think I have a computer next to the oven?

  24. Deanna Bayne says

    I made this today. It was my first time making a bechamel and it worked! I didn’t have enough course corn meal so used a half cup of corn flour to make the measurement. The polenta chilled outside (It’s October in Vancouver Canada) as the cookie sheet didn’t fit in the fridge for about 4 hours (I had left over after it was assembled). One thing I missed was cooking the flour and butter for two minutes to cook out the flour flavour on the Bechamel. Dang! I didn’t know what to do but I was drinking a glass of Rose and thought just ad a couple tablespoons so I did. It seemed to work and the flour flavour was gone. It’s all assembled outside and I will cook it in about 2 hours. I will let you know what my dinner guests think after we eat. I’m going to serve it with a simple Arugula salad on the side. I’m so excited to eat it.

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