This loaded grilled cheese sandwich packs four types of cheese, fresh vegetables, and crispy bacon between slices of sourdough bread. It combines sharp Cheddar, pepper Jack, white Cheddar, and Parmesan for a deeply savory melt. The rich, gooey cheese contrasts beautifully with the bright acidity of seasoned tomatoes and creamy avocado slices. Serve this hearty sandwich for a comforting weekend lunch or an easy weeknight dinner.