Preheat a grill pan or skillet over medium heat.
In a small saucepan, combine balsamic vinegar and honey. Bring to a simmer over medium heat and cook for 5-7 minutes until reduced and syrupy. Remove from heat and set aside to cool.
Lightly brush both sides of the ciabatta bread slices with extra virgin olive oil.
Toast the bread slices in the grill pan or skillet for 2-3 minutes per side until golden and grill marks appear. Remove from heat.
While the bread is still warm, rub one side of each slice with the peeled garlic clove to infuse a subtle garlic flavor.
On two slices of the toasted bread, layer the fresh mozzarella slices evenly.
Add the sliced heirloom tomatoes on top of the mozzarella.
Season the tomatoes with salt and freshly ground black pepper to taste.
Distribute fresh basil leaves evenly over the tomatoes.
Drizzle the prepared balsamic glaze generously over the basil and tomatoes.
Top with the remaining toasted bread slices, garlic-rubbed side down, to form sandwiches.
Cut each sandwich in half and serve immediately.