Prepare the grill with a direct hot zone and cool zone.
Soak or dip the corn with its husk still on in water then place directly over the heat. The water helps create steam to cook the corn while the husk absorbs the direct heat charring but protecting the corn inside. Cook for 10 minutes.
Corn Smear
Mix together the sour cream, cream cheese, sugar, cayenne, salt, and pepper until really smooth. Stir through the jalapeño peppers and Parmesan cheese. Let sit to combine the flavors.
Layout a sheet of foil then remove the husk from the top half of the corn to expose the yellow kernels. Cover with a quarter of the corn smear. Wrap the corn tightly in the foil. Repeat until all four cobs of corn are wrapped.
Return the wrapped corn to the cool side of the grill and leave for 5 minutes or until the smear has melted into the corn.