Cheesy Scalloped Potatoes

Steps

1. 1

   Preheat the oven to 400°F (200 °C) (200°C (400 °F)). Lightly coat an 8-by-8-inch casserole dish with nonstick cooking spray.

2. 2

   Arrange the sliced potatoes and onion rings in the prepared baking dish, staggering the rows so that potato slices and onion alternate. Keep the slices as evenly sized as possible for even cooking.

3. 3

   Place a medium saucepan over medium heat and add the butter. Melt it completely without allowing it to brown.

4. 4

   Add the flour and ½ teaspoon kosher salt to the melted butter. Whisk constantly for about 1 minute to form a smooth roux and cook out the raw flour taste.

   Start 1-minute timer
5. 5

   Pour in the room-temperature milk while whisking continuously. Cook, stirring often, until the mixture thickens into a smooth sauce.

6. 6

   Add all of the shredded cheddar cheese at once. Stir continuously until the cheese melts and the sauce is smooth, about 30–60 seconds.

   Start 1-minute timer
7. 7

   Pour the cheese sauce evenly over the arranged potatoes and onions, allowing it to flow into the spaces between the slices.

8. 8

   Cover the casserole dish tightly with aluminum foil. Bake at 400°F (200 °C) (200°C (400 °F)) for 85–90 minutes, or until the potatoes are fork-tender.

   Start 90-minute timer
9. 9

   For a crisp golden topping, remove the foil and change the oven setting to broil. Broil briefly, watching closely, until the surface is golden brown.

10. 10

    Season the finished potatoes with salt and pepper to taste. Serve hot.