01 - Place the cilantro leaves, green onions, chili peppers, and garlic cloves into a blender or food processor.
02 - Pour in the lime juice, mayonnaise, sour cream (or Greek yogurt), grated Parmesan, olive oil, white vinegar, kosher salt, and black pepper.
03 - Process on high speed until the mixture is completely smooth and creamy, stopping to scrape down the sides of the bowl as needed.
04 - Taste the sauce and adjust the salt, pepper, or chili level to reach your preferred heat and flavor balance.
05 - Transfer the sauce to a serving bowl and refrigerate for at least 30 minutes to allow the flavors to develop before serving.