1. Heat oil in a frying pan and add the onion. Add the zucchini and a bit of salt. Cook covered, for about 10 minutes.
2. Add the vegetable stock, parsley, basil and mint and simmer for another 10 minutes, until water is absorbed. Add freshly groun pepper.
4. Add cream to the zucchini and mash with a fork. You should have a creamy but not very smooth .texture
5. Meanwhile, cook the ravioli in plenty of salted water following the package instructions. When cooked, strain, mix with the sauce and serve with grated Parmesan.