In a small mixing bowl, whisk or stir together the mayonnaise, sour cream, prepared horseradish, roasted garlic, apple cider vinegar, fresh chives, Dijon mustard, garlic powder, black pepper, and kosher salt until smooth.
Cover and refrigerate until ready to serve (refrigerate for 30 minutes for optimal flavor).
Notes
Mayonnaise: Full-fat mayo or my homemade mayonnaise is best, but you can use light, plant-based, too.
Sour Cream: Again, full-fat sour cream is best here too, but it can be swapped for plain Greek yogurt for a lighter version.
Prepared Horseradish: Some brands are runnier than others, drain off excess liquid or the sauce could turn runny. For a spicier version, use "extra-hot horseradish".
Roasted Garlic:Roasted garlic gives this sauce massive flavor, if you prefer, raw garlic can be used instead, but only use one clove minced so it doesn't overpower the sauce.
Apple Cider Vinegar: Can be substituted for white wine vinegar or rice vinegar.
Store leftovers in an airtight container and keep in the fridge for up to 4-5 days, and give it a quick stir before serving.