Traditional Ham and Potato Casserole

Why This Traditional Ham and Potato Casserole Works

In the pot, butter and flour cook together first, so the flour soaks up the fat. As the milk goes in and heats up, that flour swells and thickens the milk into a smooth cheese sauce that can actually cling to the potatoes and ham instead of running to the bottom of the dish. Once the cheddar melts into it, the sauce becomes even thicker and a little stretchy, so it stays around each slice and cube.

In the oven, the sliced potatoes slowly soften as they sit in that hot cheese sauce. Starch from the potatoes seeps out into the sauce and makes it even thicker, so the layers start to hold together instead of sliding apart. The diced ham and onions are tucked between potato layers, so they stay moist while they warm through. On top, breadcrumbs and the last bit of cheese dry out and brown, forming a crisp lid. Under that crust, everything stays creamy and bubbly, and the casserole slices nicely once it cools a little.

Mistakes To Avoid

Cutting the potato slices too thick means they stay firm or even a little raw in the center while the top gets browned. The casserole then looks done on top but has hard, undercooked pieces hidden inside, and the layers don’t really meld together.

Pouring the milk into the flour and butter too fast often leaves lumps in the sauce. Those flour pockets don’t fully dissolve in the oven, so the casserole ends up with pasty, gummy bites instead of a smooth, creamy layer around the potatoes and ham.

Letting the cheese sauce get too thick on the stove can cause trouble later. A very stiff sauce doesn’t sink down between the potato slices in the oven, so the middle of the casserole stays dry and the top turns heavy and almost rubbery.

Skipping the foil in the first part of baking leads to a dried-out top and still-firm potatoes underneath. The surface browns and hardens before the heat has time to steam and soften the layers below.