Melt the butter; fry the chicken until browned on all sides. Cut the leeks into 4 lengthways, rinse out the dirt, then chopped into 1 inch pieces. Take chicken out of pan and put leeks in and fry for 5 minutes until soft.
Add the chicken, chicken stock and bouquet garni. Bring to boil, simmer for 30 minutes. Add prunes and simmer another 15 minutes.
It's now ready to eat.