In a 4 - 5 qt pan, combine onion, butter, and nutmeg. Stir often over high heat until onion is limp, 3 - 4 min.
Mix the cornstarch smoothly with a little of the chicken broth. Add to pan along with remaining broth, wine, pumpkin, and rice. Stir mixture over high heat until boiling, 3 - 4 min. Cover and remove from heat; let stand 5 min.
Stir in Parmesan cheese. Sprinkle portions with additional cheese and add salt and pepper to taste.