I place the lid on the slow cooker and set it to cook on LOW for 6-7 hours. I resist the urge to open the lid during cooking, as it lets out too much heat and steam. The casserole is done when the potatoes are easily pierced with a fork and the cheese on top is melted and bubbly around the edges. If I’m in a hurry, I can cook it on HIGH for 3-4 hours, but I find the low and slow method gives the potatoes the most tender, perfect texture. In the last 30 minutes, I’ll sometimes prop the lid open a crack with a wooden spoon to let some steam escape and help thicken the sauce.
Pro Tips for Best Results
Choosing the right potato is vital. I’ve tested this with waxy potatoes like red potatoes and russets. Russet potatoes are the clear winner. Their high starch content breaks down during the long cook, helping to thicken the sauce naturally and giving the casserole a wonderfully creamy, almost scalloped-potato texture. Waxy potatoes hold their shape better but can leave the sauce a bit thinner and separate.
Don’t skip the step of drying the potato slices. I thought it was an unnecessary fuss until I made a watery batch. The moisture clinging to the potatoes dilutes the creamy sauce, preventing it from clinging to the ingredients properly. Taking a few minutes to thoroughly pat them dry ensures your sauce is rich and cohesive, not thin and running.
For a gorgeous, browned cheese topping that you usually miss with a slow cooker, I have a little trick. About 30 minutes before serving, I’ll carefully transfer the entire insert (if it’s oven-safe) to a preheated 400°F (200°C) broiler for just 2-4 minutes. You have to watch it like a hawk, but it creates a beautiful, golden crust. If your insert isn’t broiler-safe, you can scoop portions into a baking dish to broil, or simply be content with the wonderfully melted, if not browned, cheese—it’s still delicious.
Common Mistakes to Avoid
My biggest first-time mistake was using raw, uncooked ham. I diced up a ham steak and threw it in. The ham released a ton of water during cooking, making the casserole far too wet. Don’t do what I did! This recipe is designed for pre-cooked ham—leftover holiday ham, diced ham from the grocery store, or even good-quality ham lunch meat. The cooking time is just to heat it through and infuse it with flavor, not to cook it. (See the next page below to continue…)