3 medium Vidalia onions, outer layers removed
2 tablespoons canola oil
1 leek, white part only, chopped
1 rib celery, chopped
1 quart chicken stock or low-sodium chicken broth
1/2 cup sweet sherry
1/2 cup heavy cream
1 tablespoon finely chopped fresh thyme
Salt to taste
Ground white pepper to taste
Fresh chives, for garnish

Preheat oven to 300 degrees. Wrap each onion separately in aluminum foil.
Bake 1 1/2 to 2 hours, or until onions feel tender all the way through.
Heat oil in a large pot. Add leek and celery; cook until softened but not
browned. Remove onions from foil, quarter them and add to pot. Stir in
chicken stock and sherry. Bring mixture to a simmer. Let simmer about 45
minutes. Stir in cream and thyme. Remove from heat. Puree mixture in
batches in a blender until smooth. Add salt and pepper to taste. Ladle
soup into bowls. Garnish each serving with chives. Serve immediately.