· 1 teaspoon butter, or as needed· 3 large russet potatoes, scrubbed· 2 eaches shallots· 3 teaspoons kosher salt· ½ teaspoon freshly ground white pepper· 1 pinch cayenne pepper, or to taste· 2 ½ cups grated sharp white Cheddar cheese· 1 ¾ cups sour cream
Step 1Preheat the oven to 400 degrees F (200 degrees C). Butter a casserole dish.Step 2Wrap each potato in foil and place on a baking sheet. Poke holes into potatoes using a knife.Step 3Bake in the preheated oven until very tender and easily pierced with a knife, about 1 hour and 15 minutes.Step 4Let potatoes cool to room temperature, at least 20 minutes. Unwrap. Cover with plastic wrap and refrigerate until completely chilled, 8 hours to overnight.Step 5Preheat the oven to 425 degrees F (220 degrees C).Step 6Shred potatoes into a large bowl using a cheese grater. Mince shallots to get 1/4 to 1/3 cup.Step 7Add shallots in with the potatoes; season with salt, white pepper, and cayenne. Toss with two forks until well combined. Add Cheddar cheese and mix well. Gently toss in sour cream until barely combined. Transfer mixture into the prepared baking dish, piling it up high, then patting it down very lightly.Step 8Bake in the preheated oven until piping hot and top is browned, 30 to 35 minutes.