Clean the vegetables and prepare them as described in the list of ingredients.
First sweat the onions over low heat, without fat or oil, until colorless. Gradually add the other vegetables and sweat for approx. 10 minutes. Add the water and the bay leaf, bring everything to the boil briefly and then simmer very gently for about 20 minutes. Strain the broth and season with the appropriate amount of salt.
This basic recipe results in a very tasty broth and can be adjusted to personal taste with additional ingredients in terms of spiciness, sweetness and acidity.