Mushroom Soup

15 green onions, tops and all
7 c. chicken broth
3/4 c. butter
1 1/2 lbs. fresh washed trimmed and sliced mushrooms
1/2 c. flour
Salt and white pepper to taste
2 c. half-and-half cream

Cook onions in butter for about 3 minutes. Add flour, salt, and white pepper to taste. Heat for about 10 minutes, stirring constantly. stir in mushrooms, reserving sane for garnish, and cook 10 minutes more. Slowly add heated chicken broth and bring to boil. Put through blender until smooth. Return to stove and stir in cream. Heat through but do not boil. Garnish each serving with reserved mushroom slices.