Fill a large pan with salted water, place on a high heat and bring to the boil. Meanwhile, cut the broccoli florets off the stalk and chop into nice bite-sized pieces. Set aside. Peel and trim the broccoli stalk, then add to the pan of boiling water for 5 minutes, or until just tender. Meanwhile, peel and finely chop the garlic and onion, then halve, deseed and finely chop the chilli. Using a slotted spoon, fish the broccoli stalk out of the pan, finely chop, then set aside. Place a medium pan on a medium heat with 1 tablespoon of oil, then add the garlic, onion, chilli and fennel seeds. Pick in the rosemary leaves, then fry for 8 to 10 minutes, or until softened and smelling delicious, stirring occasionally. Add the chopped broccoli stalk, then pour in the tomatoes and half a tin of hot water. Bring to the boil, then simmer for 10 minutes, or until thickened and reduced, breaking up the tomatoes with the back of a wooden spoon. Meanwhile, add the broccoli florets to the pan of boiling water and cook for 4 minutes, adding the gnocchi after 1 minute. Cook until the broccoli is tender and the gnocchi floats to the surface. Reserving a cupful of the cooking water, drain the gnocchi and broccoli, then return to the pan, off the heat. Season the sauce to taste with sea salt and black pepper, then tip it into the gnocchi pan. Toss well, adding a splash of the cooking water to loosen, if needed. Finely grate in most of the cheese, then serve with the remaining cheese grated on top.