01 - Heat a grill pan or skillet over medium-high heat.
02 - Slice each chicken breast horizontally to form thinner cutlets. Coat with olive oil and season evenly with salt and black pepper.
03 - Place chicken on the preheated grill pan or skillet. Cook for 4 to 5 minutes per side until thoroughly cooked and golden. Remove and allow to rest for 2 minutes, then slice if desired.
04 - If desired, lightly butter the inside of each roll. Toast cut sides face-down in the hot pan until golden brown.
05 - Generously spread basil pesto on the cut side of each bottom roll.
06 - Layer grilled chicken slices, mozzarella cheese, tomato slices, and arugula or spinach over the pesto. Cap with the remaining roll halves.
07 - Present sandwiches warm or at room temperature.