Scalloped Potatoes With Horseradish

Preparation

1. Step 1

   Arrange a rack in the top third of the oven and heat to 400 degrees. Peel all the potatoes (see Tip) and cut into ⅛-inch-thick slices with a sharp knife or mandoline.

2. Step 2

   In a medium saucepan, melt the butter over medium heat. Add the garlic and cook until just golden, about 1 minute. Sprinkle in the flour and whisk until a paste forms, then continue stirring to cook the flour until bubbling, 30 seconds to 1 minute more. Slowly pour in 1½ cups of the half-the-half and whisk until combined. Whisk in remaining half-and-half, the horseradish and 2 teaspoons salt. Bring to a simmer while whisking constantly, then turn off heat and let steep for about 5 minutes.

3. Step 3

   Ladle 1 cup of the horseradish cream sauce into a 9-by-13-inch baking dish, spreading to fully coat the bottom of the dish. Add half the sliced potatoes in an even layer; have fun mixing the colors. Sprinkle half the cheese on top and pour over another cup of the sauce, making sure the sauce is fully covering the cheese and potatoes. Add the remaining sliced potatoes, and top with remaining sauce and cheese.

4. Step 4

   Cover with aluminum foil and bake until potatoes are almost fully tender and sauce is bubbling, about 45 minutes. Remove the foil and continue to bake until the edges are slightly crisp and the cheese is golden brown in spots, about 10 minutes more. Let sit at room temperature for 15 minutes before serving.