Roast the tomatoes and whole, peeled garlic cloves for 30-45 minutes on a lined baking sheet, drizzled with olive oil and seasoned with salt and pepper.
Blend the tomatoes and garlic together to make a smooth sauce for gnocchi.
Boil the gnocchi for two minutes in salted boiling water and drain.
Spoon half the gnocchi into an ovenproof dish and top with half of the sauce. Gently mix them together, before topping with half the mozzarella and half the parmesan. Repeat the process until the dish is filled and parmesan covers the entire top.
Bake the gnocchi al forno in the oven for 15 minutes, and for the final two minutes, turn on the grill /broiler to crisp up the top and leave the cheese browned and bubbling.