Gram's Cheesy Scalloped Potatoes.

1/2# chedder cheese shredded.
1/4 c. margarine
5T flour
2 1/2 c. milk
1/4 c. minced onion ( I use about 1/2 Maui sweet onion diced and sauted)
1 1/2 t salt
3/4 t. pepper
7 1/2 cups sliced potatoes (1/8" thick...too thick and they won't cook well)

Make white sauce, turn off heat, add cheese, stir until melted.In a 9x13 pyrex layer sauce, potatoes, onions, potatoes, then top with remaining sauce.Bake at 350 covered for the first 45 min, then uncover for an additional 15 min.(The times here are aprox. Every cook/oven is different. And here we use recipes as guidelines not the law. When it's done, the potatoes will be tender to fork, and the cheese will be bubbly goodness.)