Ultimate Cheesy Scalloped Potatoes

Preheat oven to 400°F. Lightly grease an 8x8-inch casserole dish with nonstick cooking spray.

Create alternating layers in the prepared baking dish by arranging a layer of potatoes, followed by a layer of onions. Sprinkle each layer with a pinch of salt and black pepper, using a total of 1/2 teaspoon salt and 1/2 teaspoon black pepper.

In a medium-size saucepan, melt unsalted butter over medium heat.

Whisk in the all-purpose flour, 1/2 teaspoon salt, and 1/2 teaspoon black pepper, stirring constantly for one minute.

Gradually whisk in whole milk and continue cooking until the mixture has thickened.

Stir in shredded sharp Cheddar cheese all at once, and continue stirring until melted and smooth, about 30-60 seconds.

Pour the cheese sauce evenly over the potatoes and onions, ensuring full coverage. Cover the dish with aluminum foil.

Bake for 85-90 minutes, or until the potatoes are tender.

For a crispy topping, change the oven setting to broil after the potatoes are baked and remove the aluminum foil.

Broil until golden brown on top, keeping a close eye to prevent burning.

Remove from the oven, and let the dish rest for 5 minutes before serving.