Prepare Vegetables: Wash and slice the zucchini, red bell pepper, red onion, and portobello mushrooms into uniform ½-inch thick pieces.

Marinate: Combine the sliced vegetables with half of the extra-virgin olive oil and a splash of balsamic vinegar in a bowl. Let them sit for about 5 minutes.

Make Glaze: Whisk together the remaining olive oil, balsamic vinegar, honey, minced garlic, sea salt, and black pepper. Set aside.

Preheat Grill: Preheat your grill to medium-high heat, about 400°F (204°C).

Grill Vegetables: Place the marinated vegetables directly onto the grill, cooking for 3-4 minutes on each side until tender.

Toast Bread: Slice the ciabatta rolls in half and place cut sides down on the grill for 1-2 minutes until lightly charred.

Assemble Sandwich: Layer grilled vegetables on the bottom half of each ciabatta roll. Add mozzarella slices, drizzle with balsamic glaze, and sprinkle torn basil leaves.

Final Grill: Place assembled sandwiches back on the grill for 2-3 minutes until the cheese begins to melt and the bread is crispy.