Homemade Cheese Whiz

1 1/2 pounds American processed cheese
13 ounces evaporated milk
1 tablespoon butter
2 egg yolks -- beaten
1 tablespoon flour

In a double boiler, melt butter and add cheese. When softened, add egg yolks, milk and flour. Cook, stirring until thick. Store in a covered jar in the refrigerator.