Start by preheating your grill or a grill pan over medium-high heat. If the chicken is not yet cooked, season the chicken breasts with salt and pepper, then grill until fully cooked and juices run clear (about 6-8 minutes per side). Let it rest for a few minutes before slicing.
While the chicken is resting, slice the ciabatta rolls in half horizontally. Brush the cut sides with olive oil.
Place the rolls on the grill, cut side down, and toast for about 2-3 minutes until golden and crispy.
Spread a generous layer of basil pesto on the bottom half of each toasted roll.
Layer the grilled chicken slices over the pesto, followed by slices of tomato and mozzarella cheese.
Drizzle the balsamic glaze over the mozzarella for a burst of flavor.
Top with fresh basil leaves, and place the other half of the roll on top to complete the sandwich.
Optional: For an extra toasty sandwich, you can return the stacked sandwich to the grill for an additional 2-3 minutes on each side, or until the cheese starts to melt slightly.
Cut the sandwiches in half and serve immediately.
Notes
Serve the sandwiches on a wooden cutting board, garnished with extra basil leaves and a small bowl of balsamic glaze for dipping.