Cream of Leek Soup in the Style of Grenoble

A rich and velvety soup—fine whenever fresh leeks are available, usually year round, with best supplies in the fall and spring. (Menu and wine suggestions.) I usually prefer to begin the preparation of a rich soup with a previously prepared aromatic beef or chicken bouillon, but this one is an exception. The leeks have so much flavor to give out, and flavor of such strong character and attractive personality, that the only liquid added to them should prop