Cheesy, crispy edges are the best part of scalloped potatoes -- and using a spiralizer will give you a lot more of them. Cutting the potatoes this way makes it easy to serve everyone their own potato and creates uniform pieces that will cook at the same rate.
Preheat the oven to 350 degrees F. Grease an 8-by-8-inch square baking dish with butter.
Melt the butter in a medium saucepan over medium heat. Sprinkle in the flour and stir with a wooden spoon to make a paste. Cook until the flour mixture begins to toast, about 1 minute. Add 4 of the sage leaves and let them sizzle for a minute, then whisk in the half-and-half, nutmeg, 2 teaspoons salt and several grinds of pepper. Bring to a simmer over low heat and cook until slightly thickened, 4 to 5 minutes. Remove and discard the sage leaves, then pour 1/2 cup sauce in the bottom of the prepared baking dish and spread to coat. Sprinkle with 1/2 cup each of the Cheddar and Monterey jack.
Trim the ends from the potatoes so they will fit on a spiral slicing machine. Use the plain blade to slice a potato into a long ribbon. Pick up one end of the potato and let it spiral back onto itself in a neat pile. Tuck the spiralized potato into a corner of the baking dish, with the neat ruffly edge sticking up. Place a second potato next to the first potato, separating them with 2 of the sage leaves. Place 2 potatoes side by side in the middle of the baking dish, separating them with 2 of the sage leaves. Then place the remaining 2 potatoes and 2 sage leaves in the other corners of the baking dish, so you end up with 3 rows of 2 potatoes each. Pour the sauce over the potatoes and sprinkle with the remaining 3/4 cup each Cheddar and Monterey jack. Cover the dish with foil, tenting it so it doesn’t touch the cheese.
Bake for 1 hour. Remove the foil and continue to bake until browned and bubbly and the edges of the potatoes are crispy, 20 to 25 minutes more. Let rest for 5 minutes before serving.
Copyright 2020 Television Food Network, G.P. All rights reserved.