Cheesy Ham Potato Casserole with a Crispy Cheddar Crust Step-by-step instructions

Before you start

Before you begin cooking, organize your workspace and gather all your ingredients. Peel and dice the potatoes into uniform half-inch cubes, and dice the cooked ham to a similar size. Measure out the sour cream, melted butter, and spices.

Shred the cheddar cheese from a block and divide it into two equal portions. Preheat your oven to 375°F (190°C) and grease your nine-by-thirteen-inch glass baking dish so everything is ready for assembly.

Instructions

Sauce Preparation and Mixing

1. 1Whisk the Velvety Cream Sauce
   In a large mixing bowl, combine the condensed cream of mushroom soup, sour cream, melted unsalted butter, garlic powder, onion powder, kosher salt, and freshly ground black pepper. Whisk vigorously until the mixture is completely smooth, uniform, and velvety.
   Look for The sauce should look creamy and fully blended without any lumps.
   Tip Ensure the melted butter has cooled slightly so it does not curdle the sour cream.
2. 2Fold in Potatoes, Ham, and Cheese
   Add the peeled and diced russet potatoes, diced cooked ham, and exactly one cup of the shredded cheddar cheese to the mixing bowl. Use a rubber spatula to gently fold the ingredients into the cream sauce until every piece is evenly and thoroughly coated.
   Look for The potatoes and ham should be completely enveloped in the velvety sauce.
   Tip Dice the potatoes to a uniform size of about half an inch to ensure they cook evenly.

At the end of this phase, the potatoes, ham, and half of the cheddar cheese should be thoroughly folded into a completely smooth, seasoned cream sauce. The mixture will look thick, rich, and uniform, with no pockets of dry spices or unmixed soup, ensuring that every single bite of the finished casserole is perfectly seasoned and creamy.

Assembly and Baking

3. 3Assemble in the Baking Dish
   Grease a nine-by-thirteen-inch glass baking dish with cooking spray or butter. Transfer the potato, ham, and cheese mixture into the prepared dish, using a spatula to spread it into a flat, even layer that fills the corners of the dish.
   Look for The mixture should be level to prevent uneven cooking in the oven.
   Tip A glass baking dish is ideal as it allows you to monitor the browning on the sides.
4. 4Bake Covered and Uncovered
   Preheat the oven to 375°F (190°C). Cover the baking dish tightly with aluminum foil and bake for forty minutes. Carefully remove the foil, scatter the remaining one cup of shredded cheddar cheese evenly over the top, and bake uncovered for another fifteen to twenty minutes.
   Look for The casserole should bubble vigorously around the edges, and the cheese crust must be melted and golden.
   Tip Tent the foil slightly so it does not touch and stick to the potato mixture.

By the end of the baking phase, the casserole will be bubbling vigorously around the edges of the dish, and the top will be covered in a melted, deeply golden-brown cheddar cheese crust.

The potatoes should feel tender when pierced with a fork, and the entire kitchen will be filled with a rich, savory aroma of toasted cheese and smoky ham.

Resting and Setting

5. 5Rest and Set Before Serving
   Remove the baking dish from the oven and place it on a heat-safe surface or wire rack. Let the casserole rest undisturbed for ten minutes. This allows the hot cream sauce to cool slightly, thicken, and set, making it much easier to scoop and serve.
   Look for The bubbling will subside, and the sauce will visibly firm up.
   Tip Resist the urge to scoop immediately, as the sauce will be too runny when piping hot.

After resting for ten minutes, the vigorous bubbling will have completely subsided, and the hot cream sauce will have visibly thickened and set around the potatoes and ham. The cheese crust will be firm enough to cut through cleanly, allowing you to scoop out neat, cohesive portions that hold their shape beautifully on the serving plate.

Common mistakes

One common mistake is using potatoes that are cut into pieces that are too large, which results in undercooked, crunchy potatoes even after an hour in the oven.

Another frequent error is skipping the covered baking phase; baking the casserole uncovered the entire time will dry out the sauce and burn the cheese crust long before the potatoes have a chance to soften. Finally, avoid using pre-shredded cheese, as it will not melt into the desired gooey texture.

How to tell it’s done

To determine if the casserole is fully cooked, insert a sharp fork or toothpick into the center of the dish. The potatoes should be completely tender and offer absolutely no resistance.

Additionally, the cream sauce must be bubbling actively along the sides of the dish, and the cheddar cheese topping should be fully melted, bubbly, and beautifully golden brown across the entire surface.