3/4 c  Watercress,packed,chopped
3/4 c  Unflavored nonfat yogurt
3/4 c  Mayonnaise
1 tb Lemon juice
1/2 ts Dried tarragon leaves
1    Garlic clove
2 ts Fish sauce or anchovy paste

In a blender or food processor, combine watercress, yogurt, mayonnaise,
lemon juice, tarragon, and garlic; whirl until smooth. Add fish sauce to
taste; whirl to blend. (If sauce is made ahead, cover and chill up to a
day.) Makes about 1 1/2 cups.