Peel and slice the carrots.
Cook in boiling water for 5-7 minutes.
Drain and reserve.
Melt the butter
Cook the chopped onion until transparent.
Dice the chicken and mushrooms.
Mix the chicken, mushrooms, carrots, onions and peas in an ovenproof pie dish.
Add the flour gradually to the chicken stock, stirring until smooth.
Bring to the boil, stirring continuously
Simmer until thickened.
Stir in the milk, cream, parsley and a pinch of bay.
Season and heat, without boiling, for 2 minutes.
Pour the sauce into the pie dish.
Roll out the pastry on a floured surface.
Cut off a strip of pastry, place on the rim of the dish & moisten.
Place the remaining pastry on top.
Trim the edges
Press to seal.
Make a hole in the centre of the pastry to allow steam to escape.
Brush the top of pastry with beaten egg.
Bake at 190°C; 375°F: Gas 5 for 40 minutes, until the pastry is cooked.