Melt butter or oil in a large pan and brown the pheasants all over. Remove. Sauté the shallots and bacon. Remove from the pan. Add enough flour to the pan to take up the remaining juices. Mix well.
Add the stock, season and bring to the boil to thicken.
Return the pheasant to the pan. Add the shallots and bacon and cover. Cook in the oven at 160C/375F/Gas 5 for approx 1 hour or until the juices run clear. Add the mushrooms about 10 minutes before the end of cooking.