Preheat oven to 350˚
2 medium onions, thinly sliced
4 cups potatoes, thinly sliced
3 tablespoons butter for sauce
3 tablespoons butter for bread crumb topping
3 tablespoons flour
1 1/2 cups milk
8 ounces cheddar cheese, shredded
1 1/4 teaspoons salt
1/4 teaspoon black pepper, ground
1 cup bread crumbs
1/4 pound of diced ham (optional)
Layer onions and potatoes in a shallow baking dish then toss slightly, try not to break potatoes.
Melt 3 tablespoons of butter in a saucepan over medium heat, add flour and stir to blend well, add milk slowly, stirring constantly until sauce thickens and is smooth, add shredded cheese and ham (optional) and stir until melted. Pour sauce over potatoes and onions, mix gently.
Add 3 tablespoons of melted butter to bread crumbs and mix thoroughly. Sprinkle buttered bread crumbs over potatoes and onion mix, spread evenly.
Bake uncovered at 350˚ for 2 hours