Preheat oven to 350 degrees F. Place bread halves on a large baking sheet.
In a medium bowl, mash together garlic and butter then season with salt and pepper. Spread butter mixture onto both baguette halves. Bake until the bread is toasted, about 15-20 minutes.
Top the toasted bread with mozzarella and tomato slices and bake until the cheese has melted, about 5-10 minutes more.
Meanwhile, make balsamic glaze: In a small saucepan, combine balsamic vinegar and honey. Simmer until reduced by half, stirring occasionally, for 8-10 minutes (the mixture should coat the back of a spoon). Let cool.
Drizzle garlic bread with olive oil and balsamic glaze. Garnish with basil, then cut into slices and serve warm.