Wash and dry all vegetables. Slice the zucchini lengthwise into 1/2 inch pieces. Cut the red bell pepper into strips, slice the red onion into thin rings, and the portobello mushrooms into slices. Toss all sliced veggies into a large bowl.

In a small bowl, whisk together 2 tablespoons of olive oil, balsamic vinegar, honey (or maple syrup), minced garlic, sea salt, and black pepper until well combined.

Toss half of the prepared glaze with the sliced vegetables, coating them lightly. Allow them to rest for about 5 minutes while you preheat the grill.

Heat up your grill or grill pan over medium-high heat (around 400°F). Lightly oil the grates or pan to prevent sticking.

Grill the marinated vegetables for about 3 to 4 minutes per side, until they are tender-crisp and beautifully charred. Remove from the grill and set aside.

Brush the cut sides of the ciabatta rolls with the remaining glaze. Grill the bread, cut side down, for 1 to 2 minutes until lightly crisp and golden.

While the bread is still on the grill, place mozzarella slices on the bottom halves of the ciabatta rolls. Cover with a lid or foil to trap the heat and melt the cheese for 30 to 45 seconds.

Pile the grilled vegetables over the melted mozzarella, drizzle a little extra glaze, and scatter torn basil leaves on top. Close the sandwich and press gently.

Give the assembled sandwich a final 1-minute press on the grill to meld all the beautiful flavors together.

Remove from the grill, let rest for a minute, and serve immediately with a simple side salad or chips.