Heat the oil in a large frying pan over a low heat. Add the leeks and brussels sprouts and cook for 10-15 mins or until softened. Add the garlic and cook for 1 min. Stir through the hot stock and crème fraîche.

Cook the pasta following pack instructions. Drain and toss with the leeks and sprouts, parmesan, lemon, parsley and hazelnuts, adding a ladleful of the pasta cooking water if needed to loosen. Season to taste and spoon into four bowls.