01 -
In a cold pan, lay out the bacon and heat it up slowly on medium until it crisps. Move the bacon to a plate with paper towels while leaving the grease in the pan.
02 -
Take the bread and spread pesto on one side of each slice. Lay mozzarella, tomatoes, and bacon (if using) on two pesto-covered pieces. Cover with the other slices, pesto side in.
03 -
Warm a pan on medium heat. Smear butter onto the tops of the sandwiches, place them butter-side down in the pan. Let them cook for around 3 to 4 minutes or until golden.
04 -
Spread butter on the untouched sides of the sandwiches, turn them over, and toast the other side for another 2 to 3 minutes until the cheese is gooey and the bread is toasted. Let them cool down for 1 to 2 minutes before slicing.