Pour the stock into a saucepan and bring to the boil. Add the zucchini, reduce the heat, then cover and cook gently for 15 minutes, or until tender.
Remove from the heat, then add the garlic. Pour into a blender or food processor and blend until smooth. Return to the pan and stir in the herbs. Season to taste. Cover and keep warm, then reheat gently before serving.
Cook the pasta in a large saucepan of lightly salted boiling water for 5 minutes, or according to the packet instructions, until al dente. (Take care not to overcook the pasta, as it could break up and lose its filling.)
Drain the pasta and divide among four bowls. Ladle the soup into the bowls and serve at once.
• If the zucchini are very fresh and sufficiently young, don't peel them: you'll have a lovely deep green soup punctuated by the white of the ravioli. * • Offer a little freshly grated parmesan to sprinkle on top.