AuGratin Potatoes

4 tablespoons butter
4 tablespoons flour
2 cups milk
1½ cups grated Velveeta cheese
½ teaspoon salt
4 cups diced potatoes

Melt butter, and then add flour and mix. Add milk, stirring constantly. Add cheese and salt. Pour resulting sauce over potatoes (that have been salted and peppered). Put in a greased casserole dish. Bake at 425° for 15 minutes covered, then uncover and cook at 350° for 40 minutes.