01 - In a medium mixing bowl, combine sour cream, mayonnaise, prepared horseradish, Dijon mustard, white wine vinegar or lemon juice, salt, and ground black pepper.
02 - Stir thoroughly using a whisk or spoon until the mixture is smooth and all ingredients are evenly incorporated.
03 - Taste the sauce and adjust the horseradish level or seasoning to suit your preference.
04 - For a brighter, fresher flavor, fold in chopped fresh chives or parsley.
05 - Cover the bowl 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 as a sandwich condiment.