Place a pan with olive oil over medium heat. Add the minced garlic and saute for 1 - 2 minutes. Add the halved cherry tomatoes. Cook for 5 minutes, then add basil, stir, and cook for 5 minutes. Add in the tomato passata and water. Season with salt and pepper and cook for 15 - 20 minutes. Place a rack in the middle of the oven and preheat it to 210 °C / 410 °F.
cook the gnocchi
Place a pot with water over high heat. Season the water with salt and bring to a boil. Cook the gnocchi according to the package instructions. Drain the cooked gnocchi and preserve 120ml (1/2 cup) of cooking water.
Gnocchi alla Sorrentina
Add the gnocchi to the sauce. Add half of the preserved water from cooking the gnocchi. Only add the rest if necessary to get a creamy sauce. Toss to combine. Transfer the gnocchi to a small baking dish. Cut the mozzarella into cubes and arrange on top. Place in the preheated oven and bake for 10 - 12 minutes at 210 °C / 410 °F or until the cheese is bubbly and melted. Sprinkle with fresh basil and divide between four plates, then serve.