Sauce Verte

• ½ pint well-flavoured mayonnaise
• 1 handful each sprigs of watercress, parsley and chervil

Wash sprigs of watercress, parsley and chervil; pick them over carefully and put them in a saucepan with a little salted boiling water. Allow greens to boil for 6 to 7 minutes; drain and press as dry as possible. Pound greens in a mortar; rub through a fine sieve and add green purée to mayonnaise.