Combine onions and oil in large pot
Cook over medium heat about 3-4 minutes, stirring frequently.
Add sherry and cook 5 minutes or until onions are soft but not browned.
Add carrots, celery, and potatoes.
Cook until veggies are crisp tender.
Add chicken stock
Bring to a boil.
Cover, cook 5 minutes.
Transfer soup to blender and puree in small batches.
Return to pot and over medium heat add milk and cayenne pepper.
Season to taste with salt and pepper.