Prepare the ingredients: chop the garlic and slice the mozzarella cheese.
Heat the olive oil in a saucepan over medium-high heat. Once the oil is hot, add the garlic and cook for a minute or two until it begins to soften.
Reduce the heat to medium-low and stir in the balsamic vinegar. Cook for a few minutes and stir in the tomatoes and basil. Simmer over low heat for 10 to 15 minutes.
Transfer the sauce to an ovenproof dish and arrange the mozzarella slices on top of the sauce.
Place the sauce with cheese under a broiler for a few minutes until the cheese melts.