Dad’s Creamy & Cheesy Au Gratin Potatoes
A rich and cheesy potato casserole with a creamy sauce, topped with Gruyère and Parmesan for a golden crust.
Ingredients
Main
- 2.5 pounds Yukon gold potatoes (sliced into ⅛-inch-thick rounds)
- 0.5 medium yellow onion (thinly sliced)
Sauce
- 3 tablespoons salted butter
- 0.25 cup all-purpose flour
- 1.5 cups whole milk or unsweetened almond milk
- 8 ounces sharp Cheddar cheese (about 2 cups shredded)
- 0.75 teaspoon kosher salt (plus more to taste)
- 0.5 teaspoon garlic powder
Toppings
- 2 ounces shredded Gruyère cheese (½ cup)
- 2 ounces grated Parmesan cheese (½ cup)
Fresh chives or parsley
Instructions
- Preheat oven to 375°F (190°C). Spray a 9-inch square baking dish with cooking spray.
- Arrange potato slices and onion in the dish, leaving space for slanting slices.
- Make the sauce: melt butter, whisk in flour, then gradually add milk and simmer until thickened. Stir in Cheddar, salt, garlic, and pepper.
- Pour sauce over potatoes, cover with foil, and bake for 45 minutes.
- Remove foil, sprinkle with Gruyère and Parmesan, then bake uncovered until golden, about 30-45 minutes. Broil briefly for extra crispiness if desired. Cool 10 minutes, then garnish with chives and serve.
Notes
For extra crisp topping, broil for 1-2 minutes watching closely.