01 -
Heat olive oil in a skillet over medium heat. Add sliced onions, season with salt and pepper, and cook slowly, stirring occasionally, until golden brown and caramelized, about 15 minutes. Remove from heat and set aside.
02 -
In the same skillet, cook bacon until crispy and golden brown, approximately 5 to 7 minutes. Drain on paper towels and set aside.
03 -
Place a slice of cheese on one bread slice, top with pieces of bacon, a generous portion of caramelized onions, then another slice of cheese. Cover with a second bread slice.
04 -
Spread about 1 tablespoon of unsalted butter on the outside of each assembled sandwich.
05 -
Preheat skillet over medium heat. Cook sandwiches until bread is golden brown and cheese melts, about 4 to 5 minutes per side. Repeat for all sandwiches.
06 -
Remove sandwiches from skillet, allow to rest for one minute before slicing in half. Serve warm.