Preheat oven to 350 F. Halve the baguette crosswise, then slice each one in half horizontally lengthwise. Place the bread cut side up on a large baking sheet.
In a small bowl, blend together the butter, garlic, parsley, salt, and pepper. Spread on the baguettes and bake until golden, 12 to 15 minutes.
Meanwhile, in a small saucepan, simmer the balsamic vinegar over medium-low heat until reduced by half, about 8 minutes, unless you are using the glaze. If you are using the glaze, no need to reduce it. Let cool.
Top the toasted baguette with the tomato slices and the mozzarella and bake until cheese melts and starts to turn brown in spots, about 8 minutes.
Drizzle the garlic bread with the balsamic glaze, sprinkle with the basil, season lightly with salt and pepper and slice into pieces while still warm.
Notes
Balsamic Glaze can be drizzled over pretty much anything plain or Italian. That’s probably an oversimplification and an overstatement, but once you try it, you will be thinking of all kinds of ways to incorporate it into your meals. It’s great drizzled over cheese, fish, chicken, pork, beef, crostini, and bruschetta, and for sure, Caprese salad.