Mix together all the stuffing ingredients, then stuff the chicken cavity with it, securing it firmly.
Put the stuffed bird into a large saucepan with the sliced onion, season to taste, barely cover with water.
Add the vinegar and sugar and bring to the boil and cover. Simmer very slowly for about 2-2 ½ hours. Allow to cool in the broth and skim the top when cool.
When needed, lift the chicken from the pan, straining well. Place in a large dish and reserve the stock. Remove all the skin from the bird.
To make the sauce, melt the butter in a small pan, add flour, cook for 1 minute.
Add stock slowly, stirring until smooth and creamy.
Add lemon juice and seasoning.
Cover the bird with lemon sauce and sprinkle the lemon peel all over. Leave in a cold place.
Before serving, garnish with parsley, prunes and lemon slices.
Recipe created by Nick Fisher