Classic Cheesy Potato Casserole Recipe

A truly comforting dish, this Cheesy Potato Casserole brings together tender sliced potatoes, a rich and creamy sauce, and a generous layer of melted cheddar cheese. Finished with a crispy, golden topping, it is the perfect accompaniment to a Sunday roast, a holiday feast, or a simple family dinner. The combination of textures—from the soft, melt-in-your-mouth potatoes to the crunchy breadcrumb crust—makes this a dish that is consistently popular. This recipe provides clear, step-by-step instructions to help you achieve a perfectly cooked, flavourful casserole that is sure to become a staple in your cooking repertoire.

Ingredients

Base Ingredients

4 large russet potatoes, peeled and thinly sliced (approximately ⅛-inch thick for even cooking)
1 medium onion, finely chopped
2 cups sharp cheddar cheese, shredded
1 cup sour cream
1 cup whole milk (or skim milk for a lighter option)
1 teaspoon garlic powder
1 teaspoon onion powder
Salt and pepper, to taste

Toppings (Optional)

1 cup breadcrumbs or crushed crackers (for a crunchy topping)
4 strips of bacon, cooked and crumbled
2 tablespoons butter, melted (for the topping)

Method

Step 1: Prepare the Oven and Ingredients

Preheat your oven to 350°F (175°C). This ensures the casserole begins cooking at the correct temperature from the start. Peel the russet potatoes and slice them thinly, aiming for a uniform thickness of about ⅛-inch. Consistent slices are key to ensuring all the potatoes cook evenly, preventing some from being undercooked while others become mushy. A mandoline slicer is an excellent tool for achieving this consistent thickness. Finely chop the onion.

Step 2: Cook the Onion and Make the Creamy Sauce

In a medium skillet over medium heat, sauté the chopped onion for 5-7 minutes, stirring occasionally, until it becomes translucent and fragrant. This step softens the onion and brings out its natural sweetness, which adds depth to the final dish. Set the cooked onion aside. In a large mixing bowl, combine the sour cream, milk, garlic powder, onion powder, salt, and pepper. Whisk the mixture vigorously until it is smooth and free of lumps. This creamy sauce will bind all the ingredients together, providing moisture and flavour throughout the casserole.

Step 3: Assemble the Casserole

Lightly grease a 9×13-inch baking dish. Arrange half of the sliced potatoes in an even layer across the bottom of the dish. Scatter half of the cooked onions over the potatoes, followed by half of the shredded cheddar cheese. Pour half of the creamy sauce mixture over this layer, ensuring it seeps down into the gaps between the potato slices. Repeat the layering process with the remaining potatoes, onions, cheese, and finally the rest of the creamy sauce, poured evenly over the top. This layering technique ensures that every bite is infused with the rich, cheesy sauce.

Step 4: Add the Topping and Bake

If you are using a crunchy topping, sprinkle the breadcrumbs or crushed crackers evenly over the surface of the casserole. Drizzle the melted butter over the breadcrumbs to help them achieve a golden brown, crispy finish during baking. If desired, sprinkle the crumbled bacon on top. Cover the baking dish with aluminium foil and place it in the preheated oven. Bake for 45 minutes. This covered baking time allows the potatoes to steam and become perfectly tender. After 45 minutes, remove the foil and continue to bake for an additional 15-20 minutes, or until the top is golden brown, bubbly, and the potatoes are easily pierced with a fork.

Step 5: Rest and Serve

Once baked, remove the casserole from the oven and allow it to rest for about 10 minutes before serving. This resting period is important as it allows the layers to set, making it easier to serve neat portions and enhancing the overall presentation.

Tips & Tricks

Even Slicing is Crucial: Using a mandoline slicer is the best way to achieve uniformly thin potato slices, which is essential for even cooking.
Don’t Skip Cooking the Onions: Sautéing the onions beforehand mellows their sharpness and brings out their sweetness, adding a crucial layer of flavour that you don’t get from raw onions.
Achieving Extra Creaminess: For an even richer texture, consider adding 4 ounces of softened cream cheese to the creamy sauce mixture. Whisk it in until fully smooth for a luscious, decadent result.
Best Reheating Method: To reheat leftovers while preserving the best texture, warm them in the oven at 350°F (175°C) until heated through. Microwaving can make the potatoes rubbery.

Storage and Make-Ahead

Storage: Store any leftover casserole in an airtight container in the refrigerator for up to 3-4 days.

Make-Ahead: This is an excellent dish to prepare in advance. Assemble the casserole completely (without baking), cover it tightly with foil, and refrigerate for up to 24 hours. This allows the flavours to meld together beautifully. When ready to bake, you may need to add an extra 10-15 minutes to the covered baking time, as the dish will be starting from a colder temperature.

Variations

Gluten-Free Option: Simply use gluten-free breadcrumbs to replace the traditional breadcrumbs for the topping.
Slow Cooker Method: Layer all the ingredients in a slow cooker and cook on low for 6-7 hours or on high for 3-4 hours.
Add Vegetables: Incorporate cooked vegetables such as broccoli florets or chopped spinach between the layers for added nutrition and a pop of colour.

Serving Suggestions

This hearty casserole is delicious on its own but also pairs wonderfully with a variety of mains. It is a classic side dish for roasted or grilled meats, such as chicken, beef, or pork. To balance the richness of the dish, serve it with a simple green salad dressed with a tangy vinaigrette or a portion of steamed green vegetables. A final garnish of freshly chopped chives or parsley adds a touch of freshness and colour to the plate.