Melt the butter; fry the chicken until browned on all sides. Cut the leeks into 4 lengthways, then chop these pieces into 2.5 cm (1 inch) lengths. Reserve the green parts and shred them finely. Add the white pieces to the pan and fry for 5 minutes until soft.

Add stock and the bouquet garni. Bring to the boil, simmer for 30 minutes. Add the green leek pieces and the prunes. Simmer for another 30 minutes.

Remove the chicken, get rid of the skin and bones and cut the meat into chunks. Add the meat to the serving dish, then pour over the rest of the soup. Garnish with parsley.