Cook the pasta in salted boiling water. Reserve a mug of pasta water, then drain.
Heat some cooking oil in a pan. Season the prawns and cook for 1 to 2 minutes per side until pink. Remove to a plate.
Add the onion to the pan and cook for 5 to 6 minutes until soft.
Stir in the garlic paste, chilli paste, and tomato paste and cook for 30 seconds.
Add the chopped tomatoes. Season and simmer for 8 to 10 minutes.
Stir in the mascarpone until smooth.
Add the pasta, parmesan, and a splash of pasta water. Toss to coat.
Add the prawns back to the pan and warm through.
Stir through the parsley and finish with black pepper.
