Bring a large pot of salted water to a boil over high heat. Add the pasta and cook until tender but still firm to the bite, stirring occasionally, about 8 to 10 minutes. Drain pasta into a large bowl and reserve 1/2 cup of the cooking liquid.
In a medium skillet heat the olive oil over medium heat. Add the garlic and saute until fragrant, about 2 minutes. Add the tomatoes, salt, and pepper. As the tomatoes cook and soften, smash them with a fork. Continue to cook until the tomatoes make a chunky style sauce, about 4 minutes.
Transfer the tomato sauce to the bowl with the pasta. Toss to combine. Add the basil leaves and mozzarella. Stir to combine. Add the reserved pasta water, 1/4 cup at a time, until the pasta is moist. Serve.