Place a knob of butter into a saucepan and heat gently.
Finely chop the onion and sweat in the pan until soft and translucent.
Chop the bacon rashers into small pieces and add to the pan, along with a pinch of seasoning. Once the bacon lardons have cooked, set the whole pan to one side to cook.
Chop the chestnuts, keeping some pieces larger and chunkier than others, and slice the prunes. Add both to a large mixing bowl along with the sausagemeat, breadcrumbs, herbs, spices, beaten egg yolk and a pinch of seasoning.
Combine all the ingredients together, mixing in the cooled bacon and onion mixture.
Use to stuff into the neck or cavity of your chosen poultry centrepiece.