Make up the stuffing mix in a large bowl and set aside.
Unroll puff pastry sheet and lay on a lightly floured surface.
Preheat oven to 190C/Gas 5.
Lay nuts on an oven tray and roast for 7-10 mins (take care not to burn) and set aside to cool.
Bash to bits with a rolling pin when cool.
Melt butter and oil in a large frying pan.
Add onion and sauté until softened and golden.
Add mushrooms and continue to cook until softened.
Add chestnuts and apple and cook for 3 mins.
Add thyme leaves and Henderson’s Relish or mushroom ketchup, and season with salt and pepper.
Cook for 5 mins.
Taste and season with more salt and pepper and/or relish/ketchup to your taste.
Remove from heat and mix with the stuffing.
Place filling in a pasty shape in the centre of the pastry, leaving a border of pastry clear of filling all the way around.
Brush egg wash over the pastry border, fold the two short ends of pastry up then fold the two long sides of pastry over the filling and the ends until they meet in the middle.
Press edges together to create a pasty shape.
Brush with egg wash and use any leftover pastry to cut out holly leaf shapes to decorate.
Bake in the oven for 40 mins or until shiny and golden.
Serve hot on Christmas Day and throughout the holiday period hot or cold.
Recipe by appetite magazine at https://www.appetitemag.co.uk/nutshroom-wellington/