Portobello Mushroom Soup Recipe

1/4 cup (1/2 stick) unsalted butter
5 Leeks (white and pale green only) :
CHOPPED
1 Medium onion: CHOPPED
10 ounces Portobello Mushrooms:CHOPPED (should make four generous cups.)
1/4 cup Flour
3 cups Chicken stock or broth
4 TBS Dry Sherry
2 cups Half and Half
1/4 tsp cayenne pepper
Ground white pepper to taste

Melt butter in a heavy large pot over medium heat. Add leeks and onion; saute until soft. Add mushrooms and saute 5 min. Reduce heat to low. Add flour; cook until mixture is smooth, stirring occasionally for about 3 min. Gradually stir in stock and 2 TBS of the sherry. Bring the soup to a boil, stirring often. Reduce heat and simmer until thickened, about 10 min. Stir in Cayenne pepper. Season witht he white pepper and salt. Stir in the remaining Sherry and bring to a simmer. Serves 6.