Step 1
Place rack in center of oven; preheat to 375°. chef 12 oz. Bacon (about 12 slices), cut into 1/4-inch piecesPlace in a medium skillet and cook over medium heat, stirring frequently, until browned and crispy, 6-8 minutes. Using a slotted spoon, transfer bacon to paper towels to drain.
Step 2
3 tablespoons. Transfer bacon fat to medium saucepan; discard or reserve remaining fat for another use. Add to 6 cloves garlic, grated, 3 cups heavy cream, 1 tbsp. Add 2 tsp. diamond crystal or 1 tbsp. Morton’s Kosher Saltand 2 tsp. freshly ground peppercook over medium heat, stirring occasionally, until salt dissolves, about 1 minute (it doesn’t need to be very hot). Remove from heat.
Step 3
peel 5 pounds russet potatoes (about 10 large) Then, use a mandoline to cut into rounds about 1⁄16″ thick. Pour one-third of the cream mixture into a 13×9″ baking dish. Place the potato slices into the dish, fanning them out a handful at a time so that they overlap slightly and pressing lightly between additions to compress until all the potatoes are used and cover the bottom of the dish. Pour in remaining cream mixture; press potatoes so they are mostly submerged. Cover dish tightly with foil; bake until potatoes are tender (a tester inserted into center should give barely any resistance), 60-70 minutes. Remove foil and spread 3 oz. Sharp yellow cheddar cheese, coarsely grated (about 1 cup)finish, and continue baking, uncovered, until cheese is melted, another 6-8 minutes.
Step 4
Let the scalloped potatoes cool for 5 minutes, then top with sprinkles ⅓ cup sour cream and disperse 4 scallions, dark green part only, thinly sliced diagonallyand bacon.
To do ahead of time: Scalloped potatoes (without cheese and toppings) can be made 1 day ahead. Let cool; cover and cool. Reheat, cover and bake in 350° oven for 20 minutes, then uncover, top with cheese and cook for 7-9 minutes until melted.
