1. Simmer the pheasants in a covered pan with the stock and sherry until the meat begins to come away from the bones.
2. Remove the pheasants and allow to cool.
3. Take the meat off the bones.
4. Put the bones back in the stock and boil until you have reduced it to a thick gravy sufficient to just cover the cooked pheasant, ham and sliced mushrooms in the bottom of a deep pie dish.
5. Roll out the pastry and cover the dish.
6. Glaze with egg and bake for 30 minutes at 220°C, 425°F, mark 7.