01 -
Start with a cool skillet and cook the bacon on medium until nice and crispy. Take it out and let it drain on a plate lined with paper towels, leaving the grease behind.
02 -
Spread pesto on one side of each bread slice. On two of them, stack mozzarella, tomato slices, and bacon if you're using it. Put the other slices on top, pesto side facing in.
03 -
Warm up a skillet over medium heat. Butter the outsides of the sandwiches and lay them in the pan with the buttered side touching the surface. Let them cook for 3-4 minutes till they're crispy and golden.
04 -
Spread butter on the remaining sides, flip the sandwiches carefully, and toast for another 2-3 minutes till the bread is crisp and the cheese is gooey. Wait a minute before slicing.