01 - Place fresh cilantro leaves, stemmed and seeded jalapeño peppers, garlic cloves, and roughly chopped green onions into a blender or food processor bowl.
02 - Pour in fresh lime juice, mayonnaise, Greek yogurt (or sour cream), grated Parmesan cheese, mustard, and olive oil. Season with kosher salt and black pepper.
03 - Process on high until the mixture is completely smooth and creamy, pausing to scrape down the sides of the bowl as needed for even consistency.
04 - Taste the sauce and adjust the seasoning, adding additional lime juice or salt as desired to balance the flavors.
05 - Transfer the finished sauce to a serving bowl or airtight jar. Serve immediately alongside grilled meats, roasted vegetables, or sandwiches, or refrigerate covered for up to 3 days.