Bring a large saucepan of salted water to the boil. Heat 1 tbsp oil in a large pan over a medium heat and fry the fennel and onion for 15 mins, or until softened. Add the garlic and chilli, and cook for 1 min, then add the tomato purée and stir for 1 min more. Toss in the bacon and fry for 5-6 mins.
Meanwhile, cook the pasta according to pack instructions. Add the mushrooms to the frying pan, stir and cover for 8 mins, or until the mushrooms are soft.
Drain the pasta, adding a ladle of the cooking water to the sauce. Tip in the pasta and stir to coat. Add the rest of the oil and scatter over the parsley and Parmesan.