Sandre à l’Oseille

There are several ways of preparing pickerel with sorrel: the sorrel can be cooked with the fish, added to a separate sauce, or stuffed inside the fish, as here. Half herb, half vegetable, sorrel tastes like a sharp spinach. The nearest substitute is spinach mixed with a few leaves of watercress, and if used in this recipe both should be blanched for a minute in boiling water and then well drained before being cooked in butter.