Pre-heat oven to 350 degrees. Wash duck under cold water, pat dry. Lightly prick skin with fork. Sprinkle inside with 1 tsp. salt and 1/4 tsp. pepper. Discard giblets. Combine black olives, garlic cloves, celery, onion, and mushrooms. Stuff duck with mixture and tie legs together. Spread butter over duck. Roast duck uncovered, basting with butter drippings in the bottom of roasting pan. Cook two hours or until legs move easily at joints. Remove from oven and baste with lemon juice. Sprinkle with parmesan cheese. Return to oven and roast 10 to 15 minutes until golden.
Serve on a bed of rice moistened with gravy and garnish with mixture used to stuff duckling.