Crème de Cresson

Wash the watercress, discard the stems and reserve the sprigs; keep 12 leaves for decoration. Put the bunch of watercress in a large pot of boiling water. When the water comes to a boil, drain the watercress, rinse it under cold running water and squeeze it dry. Put the 12 leaves in a small pan of boiling water, bring back to a boil, drain and rinse them.

In a heavy saucepan melt