01 - Preheat a grill pan or skillet over medium-high heat.
02 - Slice chicken breasts horizontally to create thinner cutlets. Drizzle evenly with olive oil and season with salt and black pepper.
03 - Grill chicken cutlets for 4 to 5 minutes per side until cooked through and golden brown. Remove from heat, allow to rest for 2 minutes, then slice if desired.
04 - If desired, lightly butter the inside of each roll. Toast cut sides on the grill pan or skillet until crisp and golden.
05 - Spread basil pesto generously onto the bottom half of each roll.
06 - Place grilled chicken, mozzarella slices, tomato slices, and arugula or spinach on the pesto-covered rolls. Cap with the remaining halves of the rolls.
07 - Serve sandwiches warm or at room temperature.