Put the heart and liver in a saucepan and cover with water. Bring to the boil and simmer for 10 minutes. Chop the meat finely and set aside to cool.
Place the chopped meat in a bowl and stir in the breadcrumbs, nuts, egg, spices, herbs and celery salt.
Melt the butter in a saucepan, add the mushrooms and onion and cook over a moderate heat, stirring frequently, for about 5 minutes until softened. Stir into the meat mixture, add the sherry and season to taste.
Pack the stuffing loosely into the neck of the turkey (see