Cut each zucchini in half lenghtwise, then carefully scoop out the center of the zucchini.
Place the zucchini in a large pot of lightly salted boiling water and blanch for 2 minutes. Drain and pat dry.
Place the cherry tomatoes into a bowl, season with salt and pepper to taste. Add the garlic, basil leaves and half the amount of the extra-virgin olive oil.
Arrange the tomato slices nicely on top of the zucchini, leaving some little gaps.
Drizzle with the remaining olive oil a baking sheet, place the zucchini on top and bake in a preheated oven to 400°F/200°C for 8-10 mins. Alternatively place them on a hot grill and grill for 3 mins per side.
Add the chopped mozzarella between the tomato slices.
Place back in the oven under the broiler now, and grill for 2 mins or until mozzarella has melted and gets a nice golden crust.
Sprinkle with optional fresh basil leaves and freshly cracked black pepper, and serve