Cut the large tomatoes into 6 or 8 wedges and the cherry tomatoes in half and put them into a bowl. Add the basil leaves, olive oil, and salt and pepper, to taste. With your hand, gently mix everything together and squeeze the tomatoes a bit to release some of their juices. Cut the mozzarella into bite sized chunks and add them to the tomatoes. Gently toss to blend everything together and serve immediately.