01 - In a medium mixing bowl, whisk together the sour cream, mayonnaise, prepared horseradish, Dijon mustard, white wine vinegar or lemon juice, salt, and black pepper until smooth and uniform.
02 - Taste the sauce and adjust the horseradish quantity or seasoning to achieve your preferred level of heat and balance.
03 - For brightness, gently fold in the chopped fresh chives or parsley.
04 - Cover the bowl and refrigerate for at least 30 minutes to allow the flavors to develop and meld together.
05 - Serve chilled alongside roast beef, smoked fish, grilled vegetables, or your favorite sandwich.