01 - Preheat grill pan or skillet over medium-high heat.
02 - Slice chicken breasts horizontally to create thinner cutlets. Drizzle with olive oil and season with salt and black pepper.
03 - Grill chicken pieces for 4–5 minutes per side until thoroughly cooked and golden brown. Remove from heat, let rest for 2 minutes, then slice if desired.
04 - If desired, lightly butter the inside of each roll and toast cut sides on the grill or skillet until golden.
05 - Spread a generous layer of basil pesto on the bottom portion of each roll.
06 - Layer grilled chicken, mozzarella slices, tomato, and baby arugula or spinach leaves. Top with the other half of the roll.
07 - Serve sandwiches warm or at room temperature.