Crepe Batter: Combine eggs, milk and oil in bowl. Add flour and salt, beating well until smooth. Pour 2 tablespoons batter into greased 9-inch preheated skillet. Tilt. Cook on one side and invert onto plate. Repeat to make 20 crepes. Place 2 tablespoons sausage filling down center of each crepe and roll up. Layer rolled crepes in large baking dish. Bake at 375 degrees for 30 minutes, covered. Spoon topping over crepes and bake, uncovered, 5 minutes longer. Sausage Filling: Remove casing and crumble in skillet. Add onion and cook until done. Drain and add cheese and cream cheese, stirring until melted and ingredients are well blended. Topping: Mix butter and sour cream together. Recipe may be frozen after crepes are filled. Makes 10 servings. Cost: $5.10.