In a large saucepan, saute onion in butter until tender.
Add flour and make a paste-like mixture.
Cook and stir 2 to 3 minutes.
Add chicken stock.
Whisk in flour mixture until smooth.
Heat until boiling.
Reduce heat and simmer 20 minutes.
If desired, add more flour mixture to make soup thicker.
Add wild rice, pepper, and cream.
Simmer.
Add sherry and heat thoroughly (Makes 6 cups.)