1 cup mayonnaise
1/2 cup vinegar
2 tablespoons sour cream
2 tablespoons boiling water
1 teaspoon straight espresso powder
In a blender, combine mayonnaise, vinegar, sour cream and 1/2 cup boiling water. Blend until smooth.
Stir the hot espresso into the hot mayonnaise mixture. Reduce heat to low and blend until blended.