In a saucepan, pour a drizzle of extra virgin olive oil, add the whole peeled garlic clove, and pour in the tomato purée. Season with salt to taste and add the fresh basil leaves. Cover with a lid and cook over medium-low heat for about 30 minutes. Once cooked, ladle half of the sauce into a large mixing bowl.
Cook the gnocchi in a pot of gently simmering salted water in 2–3 batches. Ensure the water is at a gentle simmer rather than a violent rolling boil to keep the gnocchi intact. As soon as they float to the surface, remove them using a slotted spoon and transfer them directly into the bowl containing the sauce. Stir gently with a spoon to coat.
Spread the remaining tomato sauce across the bottom of a baking dish and drizzle with a little olive oil. Add an initial layer of the sauced gnocchi.
Top with a layer of diced mozzarella and a generous sprinkle of grated Pecorino. Add the remaining gnocchi, followed by the rest of the mozzarella and Pecorino. Bake in a preheated oven at 250°C (480°F) under the broiler/grill setting for about 5 minutes until melted and lightly golden. Serve immediately while piping hot!
