Begin by washing and drying your zucchini, red bell pepper, red onion, and portobello mushrooms. Slice them into uniform pieces, approximately ½-inch thick, ensuring even cooking.

In a large mixing bowl, combine half of the extra-virgin olive oil with 1 tablespoon of balsamic vinegar. Toss the sliced vegetables in this mixture until they are well-coated. Let them rest for about 5 minutes.

In a small bowl, whisk together the remaining olive oil, balsamic vinegar, honey or maple syrup, minced garlic, sea salt, and black pepper.

Preheat your grill or grill pan to medium-high heat, around 400°F (200°C). The grill should be hot enough to produce those beautiful sear marks.

Once preheated, place your marinated vegetables on the grill. Grill each side for about 3–4 minutes or until they are tender and have nice grill marks.

While the vegetables are grilling, slice the ciabatta rolls in half. After the veggies are done, place the ciabatta halves cut-side down on the grill for 1–2 minutes.

Layer the grilled vegetables generously over the toasted ciabatta halves. Add slices of fresh mozzarella on top.

Once the cheese is melted and bubbly, carefully remove the sandwiches from the grill. Drizzle a bit more extra virgin olive oil on top, and sprinkle with fresh basil leaves to finish.