10 tbsp chopped fresh parsley, plus extra to garnish
Melt 100g/4oz of the butter in a very large frying pan and fry the pieces of chicken until golden-brown. Remove the chicken with a slotted spoon and transfer to a large plate. You will need to do this in batches.
In the same pan, melt 200g/8oz of butter and fry the onion gently until soft but not browned. Add half the mushrooms to the pan, fry for 2-3 minutes until just cooked, and then drain off the excess fat and set aside. Repeat with another 200g/8oz of butter and the remaining mushrooms.
Melt the remaining butter in a large saucepan. Stir in the flour and cook for one minute, stirring constantly. Remove from the heat and gradually stir in the milk and the stock. Return to the heat and bring to the boil, stirring continuously.
Season the sauce with salt and pepper and stir in the chicken pieces, parsley, mushrooms and onions. Cook for 3-4 minutes then remove from the heat.
Sprinkle with a little fresh parsley and serve with new potatoes and vegetables of your choice