In a large soup pot over low heat, melt butter. Add flour and cook 3 minutes, stirring constantly. Add oyster liquid, clam juice, or fish broth and cook another 3 to 4 minutes or until flour is absorbed. Increase heat to medium and bring just to a boil; reduce heat to low and simmer an additional 10 minutes, stirring occasionally.
Add heavy cream; simmer 5 minutes longer, stirring constantly. Add cayenne pepper and brie cheese, stirring until cheese is melted completely.
Stir in champagne, oysters, and green onion stems. Remove from heat, cover and let stand 10 minutes. Season with salt. Serve in soup bowls.
Makes 8 servings.
* If desired, you could substitute a sparkling wine.
** Learn How To Shuck Oysters.
Oyster and Brie Champagne Soup Recipe: https://whatscookingamerica.net/Soup/OysterBrie.htm