For the basic tomato sauce, heat the oil in a wide saucepan or large frying pan, then add the garlic and basil stalks and sizzle for 1 minute, without colouring them. Stir in the tomato purée.
Tip in the chopped tomatoes, and sugar, then season with a generous amount of salt and pepper. Simmer for 5 minutes until the sauce is rich and thick. Stir in the basil leaves just before the end.
For the sausage meatballs variation, cut the sausage skin and squeeze the meat from the sausages, pinching it into small meatballs as you squeeze.
Heat the oil in a non-stick frying pan, then add the sausage meatballs and fry for 10 minutes or until browned all over and cooked through. Season with the chillies. Stir in some of the tomato sauce then bring to a simmer. Add cooked pasta to the sauce, stirring to coat it in the sauce. Add 2 tablespoons of the pasta cooking water to thin down the sauce. Serve with freshly grated Parmesan.
For the creamy mascarpone sauce variation, stir the mascarpone in to the tomato sauce until melted. Stir in cooked pasta to coat it in the sauce. Add two tablespoons of the pasta cooking water to thin down the sauce. Season to taste and serve scattered with basil leaves.