Cream of Mushroom Soup
Mastering the Art of French Cooking
1/4 cup minced onions
6-8 Tbsp butter (3+2+[1-3])
3 Tbsp flour
6 cups chicken or veal stock (or canned chicken broth with 2 sprigs parsley, 1 bay leaf, and 1/8 tsp thyme)
Salt and pepper
1 lb. mushrooms, separated into stems (chopped) and caps (sliced thinly)
1 tsp lemon juice
2 egg yolks
1/2 to 3/4 cup cream
2-3 Tbsp minced fresh chervil or parsley
Melt 3 tablespoons of butter in a saucepan. Add the onions and cook until tender but not browned, 8 to 10 minutes. Add the flour and stir over medium heat for 3 minutes without browning. Off heat, beat in the boiling stock and blend it thoroughly with the flour. Season to taste. Stir in the mushroom stems and simmer partially covered for 20 minutes or more, skimming occasionally. Strain, pressing juices out of mushroom stems. Return the soup to the pan.
Melt 2 tablespoons of butter in a separate saucepan. When it is foaming, toss in the mushrooms, about 1/4 teaspoon of salt, and lemon juice. Cover and cook slowly for 5 minutes.
Pour the mushrooms and their cooking juices into the strained soup base. Simme for 10 mintues.
Beat the egg yolks and cream in a separate bowl. Then whisk in the hot soup by spoonfuls until a cup or two has been added. Slowly add the egg mixture back into the main saucepan with the rest of the soup, continually whisking. Stir over medium heat for a minute or two to poach the egg yolks, but do not allow the soup to come up to a simmer.
Off heat, stir in 1 to 3 tablespoons of butter, one tablespoon at a time. Serve the soup garnished with the fresh chervil or parsley.