Remove the tomatoes from the vine and wash. Heat 3 tbsp of the olive oil in a large saucepan with a lid on a medium heat.
Add the tomatoes, crushed garlic and chilli flakes. Season, then heat gently, being careful not to burn the garlic, for 10-12 minutes until the tomatoes have burst. Stir gently to encourage the tomatoes to release their juices, then remove from the heat and set aside.
Cook the pasta according to the instructions on the packet. Drain, reserving 1 cup of the cooking water.
Add the cooked pasta to the tomato mix and return to a high heat. Pour in the reserved water, then add the remaining oil, half the basil leaves and the grated parmesan. Toss the pasta in the sauce until it is fully coated and the sauce begins to thicken.
Serve with the remaining basil leaves sprinkled on top as a garnish.