This recipe was taken from the book Cooking the Austrian Way.

Ingredients:

4 oz. Mushrooms
1 1/2 Tblsp butter
1 1/2 Tblsp flour
white pepper
salt
1/2 cup white wine
1 lemon
2 cups beef stock

Melt the butter in a large saucepan and blend in the flour until smooth. Heat nearly all the stock and then gradually pour it into the flour mixture, stirring constantly. Set the saucepan back over low heat to keep hot. In a small saucepan, heat a small amount of butter. Chop the mushroom caps and stems, and gently cook them in the butter with a bit of white pepper and salt. Add the remaining stock and the juice of 1 lemon, stirring constantly. Add the wine and then return the mixture to a boil, then add the first sauce, blending till smooth. Use hot.