Place olive oil and garlic in a large heavy-bottomed pot. Put on medium heat. Cook garlic until it sizzles and releases its smell, pressing it twice. Avoid browning.
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Stir in the chile pepper, then passata and a touch of salt. Boil the sauce, then reduce heat to medium-low. Let the sauce boil gradually for 20–30 minutes to thicken and taste.
2
Taste and salt as needed. Tear a handful of basil leaves and add to the sauce. Turn off heat and remove garlic. Cover to warm sauce.Preheat the oven to 400°F with a rack on the top third.
3
Add salt to a big saucepan of boiling water. Cover a large oven-proof baking dish with olive oil. Add a ladle of sauce to the dish and place near the burner.
4
If needed, gently put gnocchi into boiling water in batches. They should emerge in 30–45 seconds. Transfer half the gnocchi to the baking dish with a big skimmer or slotted spoon. Put sauce on top.
5
Add extra sauce and half the mozzarella to the baking dish with half the gnocchi. Finish cooking the gnocchi and add to the baking dish. Pour more sauce and sprinkle remaining mozzarella.
6
Cover with sauce and sprinkle with Parmigiano cheese.Bake until bubbling, 5–8 minutes. Place the baking dish under the broiler for 1-2 minutes to brown the top. Serve hot.
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