Add 2 teaspoons olive oil to a skillet over medium high heat. Saute the onion until golden and tender, about 5 minutes. Add the sliced mushrooms and saute until they're soft and golden, about 5 minutes. Add the garlic and sauté for another minute. Remove the onion mixture and set aside.
Add the ground turkey to the skillet, season with the salt, pepper, basil and oregano. Stir until well mixed and cook until crumbled and cooked through. Return the onion mixture to the pan and stir until evenly distributed.
Add the bell pepper and wine, scrapping up any browned bites in the pan. Simmer for 5 minutes. Add the tomato puree, diced tomatoes, tomato paste, crushed red pepper, and sugar. Heat to a boil; reduce heat, cover and simmer 15 - 20 minutes.
Meanwhile, add the ricotta, egg and parmesan to a bowl and whisk until combined and smooth. Stir in the spinach and season with salt and pepper. Set aside.
In a casserole dish layer the following: 1/3 of the meat sauce, 1/2 of the ricotta mixture, and 1/2 of the pasta, 1/3 of the meat sauce, 1/2 of the mozzarella, 1/2 of the ricotta, 1/2 of the pasta, 1/3 of the meat sauce.
Cover the casserole dish with foil. Bake in preheated 375 degree F oven 30 minutes. Then, sprinkle the top with the remaining mozzarella cheese. Uncover and bake 15 minutes more. Let stand 5-10 minutes before serving.
Alternatively, you can assemble the casserole in individual serving sized ramekins. Bake for 20 minutes covered, then add the cheese and bake until the cheese is melted and the dish is hot and bubbly.
Notes
Sauce can be made in advance and stored in the refrigerator for up to 2 days or in the freezer for 1 month. Cool sauce completely before freezing in an airtight container or else you will have lots of condensation from the sauce's warmth which will then cause the sauce to become watery.