Casserole in a Pumpkin

1 medium pumpkin, decorated with black marker
1 chopped onion
1 to 2 pounds ground beef
2 tablespoons soy sauce
2 tablespoons brown sugar
1 (4 ounce) can mushrooms (optional)
1 can cream of chicken soup
1 1/2 to 2 cups cooked rice
1 (8 ounce) can sliced water chestnuts (can substitute celery, chopped)

Clean out pumpkin and decorate, if desired.

Brown hamburger and onion. Drain well. Mix in remaining ingredient. Put pumpkin on cookie sheet. Fill pumpkin with meat mixture. Place in oven and bake pumpkin with lid on for 1 hour at 350 degrees F or until pumpkin is tender. Ladle out at the table directly from the pumpkin.