Combine garlic with mashed potatoes or bread in a mortar. Blend to form a soft paste. Add olive oil and vinegar alternately in very small amounts, stirring briskly. Add salt and pepper. Continue to whisk until sauce is thick.

(Blender or food processor method)

Place garlic and potatoes or bread in bowl and blend. Add olive oil and vinegar and continue to blend. If too thick, add 1/4 cup cold water. Add salt and pepper. Blend until creamy and thick.

Yield

2 cups.