01 - Preheat grill or grill pan to medium-high heat.
02 - Slice each chicken breast horizontally to create four thin cutlets.
03 - Coat chicken cutlets with olive oil, salt, black pepper, and garlic powder.
04 - Grill cutlets for 4 to 5 minutes per side until cooked through and internal temperature reaches 165°F. Transfer to a plate and keep warm.
05 - In a food processor or blender, combine basil leaves, pine nuts, garlic, and Parmesan cheese. With the motor running, stream in olive oil until the mixture is smooth. Season with salt and black pepper.
06 - Lightly toast the sliced ciabatta or focaccia rolls on the grill or in a toaster until golden.
07 - Spread 1 tablespoon pesto on the bottom half of each roll. Layer with grilled chicken, a slice of cheese, tomato slices, and arugula or baby spinach.
08 - Drizzle with balsamic glaze if desired, cover with the top halves of rolls, and serve immediately while warm.