Bring the stock to a simmer, add the mushrooms and leave them to soak and swell up. Cook the pheasant in some olive oil in a casserole until it is browned all over, then add the pancetta and brown, stirring all the time. Add the shallots and garlic and stir for a minute, then add the bay leaf. Pour in the white wine and bubble for a minute. Add the stock and mushrooms, season well and bring to a simmer. Put the lid on the pan, making sure it fits tightly, and cook gently for 1 hour until the meat starts to fall off the bones.