Best cream of mushroom soup EVER!! (for Eliza)

I'm doubling the size of the recipe i have, since it's so good, you'll want more! but if it's just for you, then halve it. Freezes well, too! on second thought, you may have to halve it, as i'm not sure double the amount will fit in a cuisinart. ah well...

Ingredients:
1 lb mushrooms, sliced (i usually use baby portobella, but regular white will do just fine...)
2 medium onions, chopped
2 cups fresh chopped parsley
28 oz (2 cans) beef broth (i usually use veggie stock that i make, but chicken stock works also)
1/2 cup butter
bit of flour
2 cups sour cream (this is the ONLY time using fat free sour cream is acceptable--i think it tastes more like mushroom sauce if you use full fat sour cream)

Saute mush, onion, parsley in butter (I didn't say it was HEALTHY soup, just yummy!) over high heat, stirring until mushrooms are limp and juices have evaporated a little bit. Stir in flour (~1 tb), remove from heat, and add stock. Bring to a boil, stirring.
Put all into large cuisinart, or large bowl and blend with one of those mixer thingies until it's finely chopped up. Add sour cream, and salt and pepper to taste, during this part.
Bon appetit!!