1)Pre-heat the oven to 200 C/ 400F / Gas mark 6.
2)Heat the olive oil in a large frying pan. Sauté the onions, garlic and mushrooms until all the juice has been absorbed from the mushrooms.
3)Add the flour and cook for a further 2 minutes.
4)Stir in the chicken stock/ soup, wine, cooked peas and parsley.
5)Put the chicken mixture in a 30 cm/ 12 inch x 22 cm/ 9 inch ovenware oval dish.
6)Roll out the puff pastry on to a lightly floured work surface (if not ready rolled) and trim to an oval about 5cm / 2 inches larger than the pie dish.
7)Cut off a 2.5 cm/ 1 inch strip from all round the oval and press onto the rim of the pie dish.
8)Brush the pastry rim with a little beaten egg, then position the pastry oval on top to make a lid. Press the edges together to seal, then using a sharp knife, knock up the edges.
9)Decorate the top with leaves made from the spare pastry trimmings, if desired. Brush the pastry all over with beaten egg.
10)Bake for 30 minutes or until the pastry is well risen and golden brown.
Serve immediately with a selection of seasonal green vegetables.