Ingredients
Method
- Preheat oven to 375°F (190°C). Melt butter in a saucepan over medium heat and cook onion 3 minutes until soft. Whisk in flour and cook 1 minute. Gradually whisk in warm milk and bring to a gentle simmer. Cook 5 minutes until thickened, then stir in salt, pepper, and thyme.
- Grease a 9×13-inch baking dish. Layer one third of the potatoes, half the ham, and one third of the sauce. Repeat with another third of potatoes, remaining ham, and another third of sauce.
- Top with remaining potatoes and pour over the last of the sauce. Spread to cover all potatoes. Sprinkle with cheddar if using.
- Cover with foil and bake 30 minutes. Uncover and bake 30 minutes more until potatoes are fork-tender and top is golden and bubbly.
- Let rest 10 minutes, then scoop generous servings while hot.
Notes
If using very salty ham, reduce added salt to ½ tsp. The casserole needs a short rest after baking to set up neatly; it may look a little loose at first but tightens as it cools.
