Duck Fat-Roasted Potatoes
3 1/2 pounds Yukon Gold potatoes, peeled and cut into 1 1/2-inch pieces
Kosher salt and pepper
1/2 teaspoon baking soda
6 tablespoons duck fat
1 tablespoon chopped fresh rosemary
Adjust oven rack to top position, place rimmed baking sheet on rack, and heat oven to 475 degrees.
Bring 10 cups water to boil in Dutch oven over high heat. Add potatoes, 1/3 cup salt, and baking soda. Return to boil and cook for 1 minute. Drain potatoes. Return potatoes to pot and place over low heat. Cook, shaking pot occasionally, until surface moisture has evaporated, about 2 minutes. Remove from heat. Add 5 tablespoons fat and 1 teaspoon salt; mix with rubber spatula until potatoes are coated with thick paste, about 30 seconds.
Remove sheet from oven, transfer potatoes to sheet, and spread into even layer. Roast for 15 minutes.
Remove sheet from oven. Using thin, sharp, metal spatula, turn potatoes. Roast until golden brown, 12 to 15 minutes. While potatoes roast, combine rosemary and remaining 1 tablespoon fat in bowl.
Remove sheet from oven. Spoon rosemary-fat mixture over potatoes and turn again. Continue to roast until potatoes are well browned and rosemary is fragrant, 3 to 5 minutes. Season with salt and pepper to taste. Serve immediately.