01 - Slice each chicken breast horizontally to create 4 thinner cutlets for even cooking.
02 - Toss chicken cutlets with olive oil, salt, and black pepper in a bowl until evenly coated.
03 - Heat a grill pan or skillet over medium-high heat. Cook chicken for 3 to 4 minutes per side until golden brown and cooked through to an internal temperature of 165°F.
04 - Place a slice of fresh mozzarella on each chicken cutlet during the last minute of cooking and cover briefly to melt.
05 - Butter the ciabatta rolls and toast cut-side down in a pan until golden, if desired.
06 - Apply a thin layer of mayonnaise to the bottom half of each roll, then spread 1 tablespoon of basil pesto over the mayo or directly onto the bread.
07 - Layer baby spinach or arugula, sliced tomato, and the warm chicken with melted mozzarella on the bottom halves. Cap with the top halves and serve warm.