This recipe is from a website called Copycat Recipes. I tried this earlier this year and it is fantastic. My husband and I love mushrooms and this hits the spot. It makes a lot so we froze some and it was even better coming from the freezer.
Beef stock: Place 2 quarts water and 2 tablespoons beef-stock base in a saucepot and simmer until beef-stock base has dissolved. Remove stock from the heat and allow it to cool until it is refrigerator temperature.
Wash all mushrooms in lukewarm water in a deep bowl. Mix the mushrooms well to loosen the dirt. Remove them from the water by hand, leaving the dirt behind.
Remove the stems from the shiitake mushrooms, and then slice all of the mushrooms ?- inch thick. Keep the button mushrooms separate from the others.
For soup :
Heat a 6-8 quart saucepot over moderately high heat. Pour in the melted butter. Add button mushrooms and diced yellow onions to hot butter and cook until mushrooms are soft.
Add the remaining mushrooms and garlic and saute for about 5 minutes, stirring constantly.
Add the sherry and cook for an additional 3 minutes.
Reduce the heat and add the flour. Using a cooking spoon, mix well and cook for 2 minutes or until butter and flour (roux) start cooking away from the sides of the saucepot.
Add half of the cold beef stock and stir until liquid thickens.
Add the remainder of the stock and spices and simmer for 10 minutes.
Add the cream and allow soup to simmer for an additional 10 minutes.