01 - Place the cilantro leaves, chopped green onions, seeded jalapeños (or Aji Amarillo), and garlic cloves into a blender or food processor.
02 - Add the mayonnaise, sour cream, fresh lime juice, grated Parmesan cheese, kosher salt, black pepper, and olive oil to the blender.
03 - Blend on high speed until the sauce is completely smooth and a vivid green color throughout.
04 - Taste the sauce and adjust the salt, lime juice, or pepper as desired to balance the flavor.
05 - Transfer to a serving bowl. For the best flavor development, chill for 30 minutes before serving, or serve immediately.