Pan fry frank with a tsp of cooking oil, turning it often until slightly browned. Cut the frank into coins. Butter the outsides of 2 pieces of bread and heat a non-stick skillet on medium. Put one piece of bread in the skillet and start to brown on the buttered side adding a slice of American cheese and some coined frank pieces. Add the other slice of cheese and top with the 2nd slice of bread with the buttered side on top/outside. Wait until the cheese starts to melt slightly before flipping over the sandwich to grill the other side. Serve warm.