Sauté the onions and celery until translucent.
Add the mushrooms, carrots, asparagus and thyme and stir-fry for 5 minutes.
Season with salt and pepper and add the cooked chicken and cream.
Let the mixture simmer for about 10 minutes or until the sauce has reduced by about a quarter.
Stir the chopped parsley through the mixture and remove from heat.
Set aside to cool down for at least 20 minutes.
Preheat the oven to 220°C.
Roll out half of your Hot Water Pastry and line the bottom of a rectangular ovenproof dish with the pastry. Spoon the filling into the pie crust.
Roll out the other half of the pastry and place on top of the filling.
Crimp the edges and cut two small holes in the middle of the pie to let out steam build-up. Use any pastry off-cuts to decorate the top of the pie.
Brush evenly with beaten egg to ensure a golden colour on your pie.
Bake for 40 - 45 minutes until the pastry is puffed up and golden brown.
Serve with rice and your choice of salad.