01 - In a medium mixing bowl, add the sour cream, mayonnaise, prepared horseradish, Dijon mustard, white wine vinegar or lemon juice, salt, and pepper.
02 - Stir thoroughly with a whisk or spoon until the mixture is completely smooth and all ingredients are evenly incorporated.
03 - Taste the sauce and adjust the amount of horseradish, salt, or pepper to suit your preferred level of heat and seasoning.
04 - For a brighter, fresher flavor, gently fold in the chopped chives or parsley.
05 - Cover the bowl tightly and refrigerate for at least 30 minutes to allow the flavors to meld and develop.
06 - Serve chilled alongside roast beef, smoked fish, grilled vegetables, or use as a sandwich spread.