In a small bowl, whisk together balsamic vinegar, garlic powder, honey, oil, and Italian seasoning and season with salt and freshly ground black pepper.
Step 2
Pour over chicken and marinate 20 minutes.
Step 3
Heat grill to medium-high. Oil grates and grill chicken until charred and cooked through, 8 minutes per side.
Step 4
Top chicken with mozzarella, avocado, and tomato and cover grill to melt, 2 minutes.
Step 5
Garnish with basil and drizzle with balsamic glaze.