Snap off and discard fibrous stem ends of asparagus. Rinse asparagus; drain. Using a sharp knife, carefully split thick asparagus stalks lengthwise.
Arrange asparagus evenly in a steamer basket. Place basket in a large skillet. Add enough water to come just below the bottom of the basket. Cover and steam for 1 minute. Remove. Arrange asparagus on an ovenproof serving dish. Top with mozzarella. Season with salt and freshly ground pepper to taste.
Broil asparagus 4 inches from the heat for 2 minutes or until cheese bubbles slightly. Sprinkle with snipped verbena or grated lemon peel before serving. Makes 4 to 6 servings.