Cook the pasta in well-salted boiling water until al dente. Reserve a mugful of the pasta water before draining.
Remove the sausage meat from the skins. Heat the oil in a large frying pan, add the sausage meat and break it into rough chunks. Fry over a medium-high heat until golden and slightly crispy.
Add the garlic and chilli and cook for about 30 seconds.
Add the tomato purée and cook for 1 to 2 minutes, stirring, until it darkens slightly.
Add the chicken stock and mascarpone then stir until smooth and creamy.
Add the pasta and Parmesan, then toss everything together, adding pasta water as needed until you have a glossy sauce that clings to the pasta.
Stir through the parsley, season with salt and plenty of black pepper, then serve with extra Parmesan over the top.