Preheat oven to 425°F (220°C).
Working carefully, cut prosciutto pieces in half lengthwise, so each piece is about 1–2 inches (2–4 cm) wide and 3–4 inches (8–10 cm) long.
Cut asparagus spears to an even length (I like to make mine about 4 inches (10 cm) long, reserving the ends for use in other recipes).
Wrap 3 spears together in 1 piece of prosciutto, and place on large sheet pan.
Drizzle with olive oil and sprinkle with black pepper.
Place in oven and cook for about 10 minutes or until asparagus is somewhat softened.
Meanwhile, in a small sauce pan, heat balsamic and garlic over medium heat until simmering.
Reduce heat and let simmer, reducing vinegar until syrupy, being careful not to burn.
Discard the garlic, and drizzle syrup over asparagus spears.
Serve immediately.