Combine oil, vinegar (a teaspoon or two at a time until balance tastes right to you)sour cream (or yogurt or mayonnaise) and Dijon mustard in a blender and turn on machine; a creamy emulsion will form within 30 seconds.
Add shallot and turn machine on and off a few times until shallot is minced within dressing.
Creamy Vinaigrette
DIRECTIONS