Slice 4 large potatoes
Slice 1 large onion
Cubes of ham, about 2 cups
1/2 stick butter
1/2 cup flour
2 cups milk
Saute 1/2 stick butter and 1/2 cup flour in saucepan, add 2 cups milk slowly, whisking constantly to incorporate until smooth. Cook for 5-10 minutes until slightly thickened.
Add 1 cup shredded sharp cheddar cheese to sauce, stir to blend.
Spray 9X12 or 10X13 pan with Pam, layer sliced potatoes, sliced onions and sauce. If you like it extra cheesy, add shredded cheese between layers as well. Cover with foil and bake at 375° for 1 hour or until potatoes are fork tender. Leave foil off for last 10 min if you want it browner.