In the jar of a blender or in the bowl of a food processor fitted with the blade attachment combine the mayonnaise, sour cream, anchovy filets, mustard, green onion, garlic, mint, tarragon, chives, and parsley. Season with salt and pepper. Process a bit, then to get the mixture really going, add the vinegar. Process until smooth, scraping down the sides of the jar or bowl, as necessary. Taste and adjust for seasoning with salt and pepper. Store in an airtight container in the refrigerator for up to 3 days.