Cut 2 pieces of parchment paper, each about 30 x 20cm. Heat the oil in a pan over a medium heat, toss in the garlic and saute for 2 mins. Fish out the garlic, then tip in the tomatoes and chilli and season. Simmer for 20 mins, stirring occasionally.
Meanwhile, preheat the oven to 180C. Cook the spaghetti for half the time given on the packet, then drain well. Add the olives and half the parsley to the tomato sauce and stir in the pasta. Taste and adjust seasoning.
Divide the spaghetti mixture equally between the pieces of paper. Scrunch the edges of each packet together to seal tightly. Put the packages in a roasting tin and bake for 7 mins until the pasta is al dente.
Transfer each package to a serving plate. Open up and sprinkle over the rest of the parsley and parmesan.