1. Lay out 4 slices of bread. Divide ½ the cheese among 4 slices of bread. Top with sliced apples, bacon then remaining cheese. Combine Dijon, mayo and spread on remaining 4 slices of bread.
2. Heat cast iron pan, sauté pan or griddle over medium-high heat. Liberally coat both sides of bread with butter, place on griddle or sauté pan and lightly brown. Flip to cook other side and cook until golden brown and flip one more time. Cut sandwiches on a bias and serve.