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.