01 - Preheat a grill pan or skillet over medium-high heat.
02 - Halve chicken breasts horizontally to create thin cutlets. Drizzle with olive oil and season both sides with salt and black pepper.
03 - Grill chicken cutlets for 4 to 5 minutes per side, until fully cooked and golden brown. Remove from heat, rest for 2 minutes, and slice if preferred.
04 - If desired, lightly butter the cut sides of each roll. Toast on the grill or skillet until golden and crisp.
05 - Spread a generous layer of basil pesto onto the bottom half of each toasted roll.
06 - Layer with grilled chicken, fresh mozzarella slices, tomato, and arugula or spinach. Cover with the top half of the roll.
07 - Serve the sandwiches warm or at room temperature.