Makes 4.
To a saucepan over low heat, add the balsamic vinegar. Bring to a simmer and allow to reduce until it is thicker enough to coat a spoon, about 3 minutes. Turn off the heat and set aside.
Preheat your broiler to high. Place the slices of Italian bread on a rimmed sheet pan. Drizzle each slice of bread evenly with olive oil. Toast the bread under the broiler until golden brown, watching it carefully. Remove the bread from the oven and rub the cut-side of sliced garlic across the toasted side of each slice of bread. Place three balls of mozzarella onto the hot toast. Lay 2-3 slices of nectarine onto each piece of bread. Distribute the strips of prosciutto evenly on each. Sprinkle with fresh bail leaves. Using a spoon, drizzle each piece of bruschetta with the balsamic reduction. Season with salt and pepper to taste. Serve promptly while warm.