Extra-Cheesy Cheddar Potatoes Au Gratin

Unbalanced

% Daily Values based on a 2,000 calorie diet

Step 1

Preheat the oven to 375°F. Generously butter 9×13-inch baking dish.

Step 2

Scrub the potatoes. You can peel them if you prefer, but with yellow potatoes I would leave the thin skins on. Slice them approximately ⅛-inch thick. A mandoline is ideal. Don't rinse the potatoes after slicing. Their starch will help the sauce thicken.

Step 3

Place the sliced potatoes in a large microwave-safe bowl. Cover loosely with a microwave-safe lid or plate. Don't add water. Microwave on HIGH for 4 minutes. Carefully uncover and gently toss/turn the potatoes so they heat evenly. Cover again and microwave another 2–3 minutes. You're not trying to cook them completely. The slices should be warm, somewhat flexible and beginning to soften but still have some firmness when pierced. Set aside while you make the cheese sauce.

Step 4

Melt 2 Tbsp butter in a medium saucepan over medium heat. Add the garlic and cook for about 30 seconds, just until fragrant. Whisk in 2 Tbsp flour and cook, whisking continuously, for 1 minute. Gradually whisk in the 1 cup skim milk, followed by the 1 cup heavy cream. Add: ¾ tsp kosher salt, ½ tsp black pepper, and ¼ tsp onion powder. Cook over medium to medium-low heat for about 3–5 minutes, whisking frequently, until it begins to thicken. It should lightly coat a spoon but still be quite pourable. Don't cook it into a thick gravy—the potatoes will absorb liquid during baking.

Step 5

Remove the saucepan completely from the heat. Gradually stir in: 2 cups sharp cheddar and ½ cup Parmesan. Add the cheese a handful at a time, stirring until melted before adding more. You should now have a rich, smooth cheese sauce. Reserve the remaining ½ cup cheddar for the top.

Step 6

Arrange approximately ⅓ of the potatoes in an overlapping layer in the baking dish. Spoon about ⅓ of the cheese sauce evenly over them. Repeat with another third of the potatoes and sauce. Finish with the remaining potatoes and remaining sauce. Gently press down on the potatoes with the back of a spoon or spatula. You want the cheese sauce to settle down between the layers.

Step 7

Cover the dish tightly with aluminum foil. Bake at 375°F for 35–40 minutes. At 35 minutes, insert a thin knife into the center of the casserole. It should pass through the potatoes very easily, with essentially no resistance. If they're still noticeably firm, cover again and bake another 5–10 minutes. Don't uncover them for the final browning until they're completely tender.

Step 8

Once the potatoes are tender, remove the foil. Sprinkle the reserved ½ cup sharp cheddar evenly over the top. Bake uncovered for 15–20 minutes, until the cheese is melted, the sauce is bubbling around the edges, and the top has some golden-brown spots. For a more browned top, you can broil for 1–2 minutes at the very end. Watch it continuously.

Step 9

This part matters: let the potatoes rest for 15 minutes before serving. Straight from the oven, the cheese sauce may look a little loose and molten. During the rest, the potatoes continue absorbing some of the sauce and the cheese sauce thickens. You should end up with very tender potatoes, plenty of thick cheddar-Parmesan sauce between the layers, and a gooey browned cheddar top.