Cook the pasta in a large pan of lightly salted boiling water, for 10 to 12 minutes.
While the pasta is cooking, heat a dash of oil in a large frying pan and add the garlic. Stir for a few seconds until it is lightly golden but not burnt. Add the fresh tomatoes, oregano, tomato purée and the tinned tomatoes.
Cook over a medium heat for 5-8 minutes, adding a ladleful of the pasta water when the sauce gets sticky. You should get a thick sauce.
Add the basil leaves and the mascarpone, turn off the heat, then stir until you get a creamy, glossy sauce.
The pasta should be ready by now, so drain it then tip into the sauce. Toss all together so that the pasta is well coated with the sauce.
Serve with grated Parmesan and freshly ground pepper.