Slice the ciabatta or sourdough loaf horizontally to create the top and bottom of the sandwich. If the loaf is large, cut into portions for individual sandwiches. Optional: lightly rub the cut surfaces with the halved garlic clove for a subtle garlic aroma.

Prepare mozzarella

Slice the fresh mozzarella into 1/4-inch (about 6 mm) thick slices. Pat slices dry with paper towel to remove excess moisture so the sandwich doesn't become soggy.

Prepare tomatoes

Slice the ripe tomatoes into 1/4-inch (about 6 mm) thick slices. If tomatoes are very juicy, lightly salt and let sit on a paper towel for 5 minutes, then blot to remove excess juice.

Season tomatoes

On a small plate, combine salt and black pepper. Lightly sprinkle the salt and pepper over both sides of the tomato slices to season them.

Assemble sandwich

Drizzle 1 tablespoon extra-virgin olive oil over the bottom half of the bread. Layer tomato slices evenly over the oil. Place mozzarella slices in a single layer on top of the tomatoes. Tuck fresh basil leaves between the mozzarella slices so leaves make contact with cheese and tomatoes. Drizzle the balsamic glaze evenly over the mozzarella and basil (use more or less to taste). If desired, drizzle the remaining 1 tablespoon olive oil over the top layer.

Finish and press

Place the top half of the bread over the stacked ingredients. Press down gently to compress the sandwich slightly so the flavors meld and the sandwich is easier to eat.

Optional: Grill or toast

If you prefer a warm, slightly crisp sandwich, heat a skillet or grill pan over medium heat. Brush the outside of the sandwich lightly with butter or olive oil. Place sandwich in the pan and cook 2–3 minutes per side, pressing gently with a spatula or weighted press, until bread is golden and cheese softens (do not overheat or mozzarella will fully melt and run). Remove and let rest 1 minute before cutting.

Slice and serve

Using a sharp serrated knife, cut the sandwich into portions. Serve immediately while bread is crisp and ingredients are fresh. Adjust seasoning with extra salt, pepper, or additional balsamic glaze to taste.