In a medium pot, cover potato cubes with cold water. Toss in garlic cloves and 1 teaspoon salt. Place on high heat and bring to a boil. As soon as the potatoes boil, remove from heat and drain well in a colander.
In a large (12-inch) cast iron pan or heavy-bottomed skillet, heat olive oil and duck fat over high heat. When small bubbles begin to rise (but before oil is smoking) and oil is very hot, add rosemary. Stir carefully with tongs for a minute.
Add potatoes and garlic cloves all at once to the hot, fragrant oil and carefully arrange them with your tongs so that they are evenly distributed around the pan. Place the skillet on the bottom shelf of the hot oven and roast for 5 minutes. Remove pan from oven and carefully stir the hash browns so they have a chance to brown evenly. Return to oven for another five minutes.
Remove potatoes from oven and place on a stove burner set to medium high. Blast the potatoes for 2-3 minutes, stirring continually, until they become a dark golden brown. Remove from heat.
Using a slotted spoon, transfer the potatoes to a serving bowl. Sprinkle with fresh chopped rosemary, if desired, and serve at once.
Cool the oil, then strain and reserve for another use.
These will be the most popular item on your brunch table, guaranteed. Serve them with a side of malt vinegar to really take it to the next level. Oh, and in this recipe the garlic is boiled with the potatoes, which softens its pungency. No one likes too many aggressive flavours in the morning! Duck fat can be found in the frozen section of most butcher shops. It adds fantastic flavour to the potatoes, but olive oil can easily be substituted.Freezing Tip: Both of these potato side dishes should be served immediately, but they also reheat nicely in a blazing hot oven. Should you wish to freeze the hash browns for convenience sake, place them in a single layer on a parchment paper-lined cookie sheet and freeze them until solid. Transfer the hash browns to a sturdy resealable plastic bag and remove as much air as possible. Hash browns will keep, frozen, for 8 weeks.