Ingredients
Vegetables
- 4 russet potatoes, peeled and sliced into ¼-inch slices (about 2 pounds)
- 1 yellow onion, sliced into rings
Dairy and Butter
- 3 tablespoons unsalted butter
- 2 cups whole milk, room temperature
- 1 ½ cups mild cheddar cheese, shredded
Dry Ingredients
- 3 tablespoons all-purpose flour
- ½ teaspoon kosher salt
Seasonings
- salt and pepper to taste
Instructions
- Preheat Oven: Preheat your oven to 400°F (204°C). Lightly spray an 8×8-inch casserole dish with nonstick cooking spray to prevent sticking.
- Arrange Potatoes and Onions: Layer the peeled, thinly sliced potatoes and onion rings alternately in the prepared baking dish, creating a staggered pattern for even distribution and flavor.
- Prepare Cheese Sauce: In a medium saucepan over medium heat, melt the unsalted butter. Whisk in the all-purpose flour and kosher salt continuously for one minute to create a roux without lumps.
- Add Milk and Thicken: Gradually stir in the room-temperature whole milk, continuing to whisk until the mixture thickens into a creamy sauce, ensuring there are no lumps.
- Melt Cheese into Sauce: Remove the sauce from the heat and stir in all the shredded mild cheddar cheese at once. Keep stirring for 30 to 60 seconds until the cheese is fully melted and the sauce is smooth.
- Combine and Cover: Pour the prepared cheese sauce evenly over the layered potatoes and onions. Cover the casserole dish tightly with aluminum foil to lock in moisture during baking.
- Bake: Place the covered dish in the preheated oven and bake for 85 to 90 minutes, or until the potatoes are tender when pierced with a fork.
- Broil for Crisp Topping: For a golden and crisp cheese topping, remove the foil and change the oven setting to broil. Broil the potatoes carefully until the cheese on top achieves a nice golden-brown color, watching closely to prevent burning.
- Season and Serve: Season the scalloped potatoes with salt and pepper to taste. Serve hot as a deliciously cheesy side dish.
Notes
- For uniform potato slices, use a mandoline if available, but be cautious to avoid injury.
- You can substitute mild cheddar with sharp cheddar for a more pronounced cheese flavor.
- Allow potatoes to reach room temperature after slicing for even cooking.
- To prevent the cheese sauce from separating, avoid overheating once cheese is added.
- Broiling time is short—watch carefully to avoid burning the topping.
- Prep Time: 15 minutes
- Cook Time: 1 hour 30 minutes
- Category: Side Dish
- Method: Baking
- Cuisine: American
- Diet: Vegetarian
