Ham and potato casserole

While it hasn't been particularly cold this winter here in Dublin, who can resist a good casserole on a gray, drizzly day? This dish is pretty versatile, and we often use whatever leftover meat we have on hand, although I do think ham is best, (but smoked sausage is also delicious). I have been known to replace the onions with leeks (very tasty) or sometimes I will also throw in a bit of cauliflower or brocolli. But it's also delicious prepared exactly as described; this is total comfort food at its best.

Ham and Potato Casserole

½ pound cooked ham, cut into medium-small cubes
2 teaspoons dijon mustard
1 large onion, thinly sliced
2 tablespoons butter
2 pounds potatoes, medium dice, boiled
bread crumbs, mixed with a little melted butter

Sauce:
2 tablespoons butter
2 tablespoons flour
2 cups milk (or 1 cup milk and 1 cup cooking water from potatoes)
8 oz cheddar cheese (could also use gruyere or swiss, or a combination of cheeses)

Heat oven to 350°. Toss ham with mustard in a medium sized casserole dish. Let sit while you cook the onion in 2 tbsp butter and a bit of salt and pepper until translucent. Mix onions in with ham, then gently fold in cooked potatoes.

Make sauce: Melt butter over medium-low heat, add flour, then add the milk (to lighten the dish up a bit, you can also make the sauce using the water that you used to cook the potato in), whisking quickly to avoid lumps). Let thicken a bit, then add cheese. Cook until sauce has thickened, 2 or 3 minutes.

Pour sauce over ham mixture, and stir very gently just until combined. Top with buttered breadcrumbs. Bake for 45 minutes.

Recipe from Gwyneth, from a potato cookbook I found years ago