1) Preheat the oven to 200c Gas 6 2) Heat a large ovenproof frying pan until hot, add the butter and when foaming, add the shallot and garlic and fry for a minute. 3) Add the chicken and fry until lightly browned. 4) Slice the mushrooms into 3 and add to the pan, fry over a high heat for 2-3 minutes, or until just softened. 5) Add the Madeira and flambé by tipping the pan towards the flame. Allow to die down. 6) Add the chicken stock and bring to a simmer, then add the tarragon and cream and simmer for five minutes. 7) Add salt and pepper to taste and then set aside to cool. 8) Roll out the pastry on a floured surface, until it is the same diameter as the frying pan and about 4-5mm thick. 9) Lay the pastry over the top of the pie filling and tuck the edges around the filling. Brush the top of the pie with the remaining egg. 10) Bake for 25 minutes, or until the pastry is crisp and golden-brown and the filling bubbling.