Wash and slice the zucchini, red bell pepper, red onion, and portobello mushrooms into even ½-inch thick pieces.

Whisk together extra-virgin olive oil, balsamic vinegar, honey (or maple syrup), minced garlic, sea salt, and black pepper until well combined.

Toss the sliced vegetables with half of the balsamic mixture, coating them evenly. Let marinate for about 5 minutes.

Preheat your grill or grill pan to medium-high heat, aiming for about 400°F.

Place the marinated veggies on the hot grill and cook for 3-4 minutes per side until tender with char marks.

Brush the ciabatta rolls with the remaining balsamic mixture and toast cut-side down on the grill for about 1-2 minutes.

Layer the grilled vegetables and slices of fresh mozzarella on the bottom half of each roll.

Top with the other half of the ciabatta, return to the grill for an additional 1-2 minutes until cheese melts.

Remove from the grill and garnish with fresh basil leaves and drizzle with extra virgin olive oil before serving.