THIS ALSATIAN specialty is quick and easy to prepare. Classically, poulet au Riesling was made by simmering the chicken in a combination of wine and water. The resulting stock was thickened to make a velouté sauce, which was further enriched with egg yolks and cream. Mushrooms were poached separately and their liquid reduced and added to the sauce. In this recipe, the mushrooms are cooked with the chicken, eliminating two steps, and only cream is used in the sauce. Omitting the butter, flour, and egg yolks yields a smaller quantity of sauce with a greater intensity of flavor.