Place the fresh mozzarella in a sieve over a bowl for approximately 20 minutes. Carefully hollow out the mozzarella and chop the excess mozzarella.
In a medium bowl combine, chopped excess mozzarella, chopped tomatoes, onion and celery, oregano, salt, chopped basil, olive oil and balsamic vinegar, toss gently together.
Fill the hollowed out fresh mozzarella with the caprese mixture and drizzle with a little olive oil, serve the extra caprese mixture on the side. Serve immediately. Enjoy!