Au gratin Potatoes

12 medium potatoes
8 tablespoons butter or margarine
8 tablespoons flour
1 teaspoon salt
Pepper
4 cups milk, heated
2 cups shredded cheese

Cut up potatoes and cook until just tender. Melt the butter in a saucepan and stir in the flour and salt and pepper. Gradually add the milk, stirring constantly. Cook over low heat and continue stirring until the sauce thickens. Put ½ of the potatoes in a casserole dish, top with 1 cup cheese and half of the sauce. Add the remaining potatoes top with ½ cup cheese and remaining sauce. Top with remaining cheese. Bake at 375F or 190C for about 15 minutes or until cheese melts. Makes 12 servings.