Oven Creamed Potatoes

6 medium potatoes (cooked and diced)
1/4 cup butter
1/3 cup flour
3/4 tsp. salt
1/4 tsp. prepared mustard
1/4 tsp. black pepper
2 cans evaporated milk
3/4 cup cheddar cheese (grated)

In a saucepan, over very low heat, melt butter and stir in flour, salt, pepper, and mustard.

Slowly add milk a little at a time and cook, stirring constantly until it thickens.

Put mixture into a 1 1/2 quart casserole then layer potatoes on top. Sprinkle cheese over the potatoes.

Bake at 375° F. for 45 minutes.