Heat the oil in a large skillet over medium-high heat. Add garlic, tomato sauce, basil and salt, and cook for 5 minutes.
Preheat the oven to 200° C. Bring a large pot of salted water to a boil. Carefully add the gnocchi to the water and cook for 1 minute, then drain.
Pour the gnocchi into a pan, add the sauce and grated Parmigiano Reggiano. Finally add the diced mozzarella and some basil leaves.
Bake until bubbly, 10-15 minutes. Garnish with additional basil leaves.