Potato and Leek Soup

The potage bonne-jemme of the cookbooks (finely sliced leeks and potatoes stewed in butter, moistened with consommé, usually but not always puréed, and finished with milk and either butter or cream—or with both)—that soup which, chilled and richly creamed, has become the American vichysoisse—would come as a surprise to the bearers of the tradition from which it is borrowed. The potato and leek soup that is prepared night after night in the kitchens of nearly every Parisian concier