Cut the pheasant into eight pieces. Slice the onions and mingle with the pheasant, salt and pepper. Leave to stand for three hours or overnight in a cool place. Chop the giblets finely. Remove the onions from the pheasant and cook them in the butter until golden. Add the giblets, thyme and parsley, and stock, and simmer on a low heat. Carefully fry the pheasant pieces in a little cooking oil for about five minutes, turning occasionally. Put the pheasant and onion gravy together in a casserole and cook at 350°F, 180°C, gas mark 4 for one hour twenty minutes.