The flavor of this fish stock is enhanced by adding fennel, orange and lemon zest, and all the good herbs of Provence. Make extra and freeze it for future use.
Melt the butter in a large saucepan. Add the leeks, fennel, orange and lemon zest, bay leaves, herbs and spices, and cook 10 minutes. Stir in the flour, and cook 1 minute.
Add the water, wine, fish trimmings, and salt, and heat to a boil. Reduce the heat and simmer 30 minutes. Strain, and allow to cool before refrigerating or freezing.