Once the chicken is cool, discard the skin and remove the meat from the bones.
Chop the chicken into small pieces and transfer to a bowl.
Chop the onion and carrot and add to the chicken.
Now bring the stock back to the boil and let it bubble for 10-15 minutes to reduce it. Add the peas to the stock and let them cook for 2-3 minutes then use a slotted spoon to remove them from the stock and add to the chicken and vegetables.
Pour out 300ml (½ pint) of the stock and into a jug and set aside.
To make the creamy sauce, first melt the butter in a saucepan.
Stir in the flour to create a paste.
Now use a whisk to stir in the stock.
Season it well and then stir in the cream.
Pour the sauce over the chicken and vegetables, mix well and transfer the filling into a pie dish.