Prepare the goose, mix together the butter, salt and pepper, and place this in the body.
Truss the bird, and cook in a moderate oven (350°-375° F., Gas 4-5) for about 1 hr., basting with fat if necessary.
Dish the bird.
Garnish with the watercress.
Brown gravy and gooseberry jelly, or gooseberry sauce may be served, if desired.