To roast the chestnuts, cut an X on the flat side of each chestnut and bake 15 to 20 minutes at 190C oven. Let cool for 10 minutes and then peel and chop.
In a large pot over low heat, heat the butter then add onions. Sauté for about 3 minutes or until soft. Meanwhile lightly grind sage, rosemary, thyme and pepper together.
Stir in minced garlic, chestnuts, mushroom, herbs and spice mix and sauté for a further 4-5 minutes.
Beat egg and milk together and pour over cubed bread.
Drizzle bread with warm broth and toss to ensure even coverage.
Toss through cooked mixture gentle with your hands to coat everything well.
Set aside to cool.
Spoon some stuffing loosely in neck cavity, pull neck skin over stuffing and fasten to turkey’s back with a short skewer. Loosely spoon stuffing into body cavity, tuck the legs under the band of skin that crosses the tail or reset the legs into the leg clamp. Or tie the legs to the tail with kitchen string. Twist the wing tips under the back.