01 - Heat grill pan or skillet over medium-high heat.
02 - Slice chicken breasts horizontally to form thin cutlets. Drizzle with olive oil and season evenly with salt and black pepper.
03 - Grill chicken cutlets for 4 to 5 minutes on each side until fully cooked and nicely golden. Remove from heat and rest for 2 minutes before slicing if desired.
04 - If desired, lightly butter the inside of each roll. Toast cut sides on the grill pan or skillet until golden brown.
05 - Spread a generous layer of pesto onto the bottom half of each roll.
06 - Layer grilled chicken, mozzarella slices, tomato, and baby arugula or spinach on the prepared rolls. Close with the top half.
07 - Serve sandwiches warm or at room temperature.