1) Cook chicken. Pour the wine and a liter of water into the pan, add the chicken, the scraped carrot, a teaspoon of salt and simmer for an hour.
2) Make it open the mussels. Peel and slice the onions, passes mussels under cold water, remove the filaments from the celery and keep the leaves aside. Put it all in
pan with a glass of water, bay leaf and 2-3 peppercorns. Cover and cook over high heat for 5 minutes or until the mussels have opened. Remove the shellfish, filter the cooking liquid.
3) Complete. Drain the chicken with a slotted spoon, cut the pulp into chunks and put them back into the pan. Clean the leeks by removing rootlets, green parts and outer sheaths, add them to the chicken together with a little cooking liquid from the mussels, bring back to the boil, then add the cornstarch dissolved in a little liquid from the mussels and cook until the soup thickens. Add the cream, the mussels, mostly shelled, and the saffron. Leave on the fire for a couple of minutes and serve. Garnish with the celery leaves kept aside.