Ingredients
- 4 russet potatoes, peeled and sliced into ¼-inch slices (about 2 pounds)
- 1 yellow onion, sliced into rings
- 3 tablespoons unsalted butter
- 3 tablespoons all-purpose flour
- ½ teaspoon kosher salt
- 2 cups whole milk, room temperature
- 1 ½ cups mild cheddar cheese, shredded
- salt and pepper to taste
Instructions
- Preheat oven to 400°F. Lightly spray an 8×8-inch casserole dish with nonstick cooking spray.
- Arrange the potatoes and onions in the prepared baking dish, staggering potato and then onion.
- In a medium-size saucepan, melt butter over medium heat. Mix in the flour and salt, and stir constantly with a whisk for one minute. Stir in milk. Cook until mixture has thickened.
- Stir in cheese all at once, and continue stirring until melted and smooth, about 30-60 seconds.
- Pour the cheese sauce over the potatoes, and cover the dish with aluminum foil.
- Bake for 85-90 minutes, or until the potatoes are tender.
- For a crisp topping, change the oven setting to broil after the potatoes are baked. Broil until golden brown.
- Season with salt and pepper to taste and serve.