Melt butter, add flour, blend until smooth. Gradually add milk, bring to a boil stirring constantly. Cook about 3 minutes until smooth and creamy. Stir in Chez-Whiz, salt and pepper. Remove from burner after cheese melts.
Pour layer of sauce in buttered baking dish, thne add layer of sliced potatoes. Alternate layers until dish is full. Top layer should be of sauce. Sprinkle with buttered cracker crumbs on top and bake at 35o degrees for 30 minutes.