Watercress Soup with Sea Scallops and Osetra Caviar

In Alain Ducasse’s monumental new cookbook Grand livre de cusine, this soup appears as Cresson de fontaine, but he also calls it a velouté. He’s not referring to velouté as the soup classically thickened with flour and butter and cooked for hours to obtain a velvet texture, but to the texture itself—slightly thick and certainly velvety.

As for the osetra caviar, it comes from a sturgeon n