In A Large Skillet, Melt Butter Over Medium High Heat. Crack Eggs In Pan And Cook To Desired Firmness. Just Before Eggs Are Cooked, Place A Slice Of Cheese Over Each Egg. After Cheese Has Melted, Place Each Egg On A Toasted Slice Of Bread. Season Eggs With Salt And Pepper. Spread Mayonnaise And Ketchup On Remaining Slices Of Bread And Cover Eggs With Bread To Make 4 Sandwiches. Serve Warm.