Gently cook the carrots and celery in the oil in a large saucepan for 20 mins, until soft. Splash in water if they stick. Add the sugar,, purée, herbs and zucchini/courgettes and cook for 4-5 mins on a medium heat until they brown a little.
Pour in the tomatoes and stock, then simmer for 20 mins. If you’re freezing it, cool and do so now (freeze for up to three months). If not, add half the Parmesan and the pasta and simmer for 6-8 mins until pasta cooked.
Sprinkle with basil and remaining Parmesan to serve. If frozen, defrost then re-heat before adding pasta and cheese and continuing as above..