01 - Slice each chicken breast horizontally to create 4 thinner cutlets for even cooking.
02 - Toss the cutlets in a bowl with olive oil, salt, and black pepper until evenly coated.
03 - Heat a grill pan or skillet over medium-high heat. Cook the chicken cutlets for 3 to 4 minutes per side until golden brown and cooked through to an internal temperature of 165°F.
04 - During the final minute of cooking, lay a slice of mozzarella on each cutlet and cover briefly to melt.
05 - Butter the cut sides of the ciabatta rolls and toast in a pan until golden and crisp.
06 - Spread a thin layer of mayonnaise on the bottom half of each roll, then layer 1 tablespoon of pesto over the top.
07 - Stack baby spinach or arugula, sliced tomato, and the warm chicken cutlet with melted mozzarella on the bottom half of each roll.
08 - Place the top half of each roll over the assembled layers and serve immediately while warm.