1. Pour the very hot broth, bring to a boil, then reduce the heat and let simmer for 25 minutes. Pass through a mill or blender.
2. Peel and wash all the vegetables, peel and slice the onion, cut the vegetables into rounds.
3. In a large saucepan, melt the onion in a little olive oil or butter. Add the vegetables, then let them cook for 2 minutes.
4. Add pepper (no salt, as the broth is already seasoned), a small pinch of ground chili pepper for a kick. Serve hot with parsley or chervil.