Prepare creamy spread for corn: Chop cilantro. Mix mayo, sour cream, cilantro, garlic and a squeeze of lime. Set aside.
Place corn on the grill on med/high heat. Close cover and grill 15 to 20 minutes, turning about every 5 minutes until all sides are grilled. Corn is ready when piercing with a knife and kernels are tender.
Remove husks. Butter corn. Add some creamy spread to corn, squeeze some fresh lime, and sprinkle with parmesan cheese and chili powder. Enjoy.