Bring water and salt to a boil in a large saucepan over high heat. While whisking continuously, slowly pour in polenta. Continue whisking for 5 minutes, adjusting the heat as necessary.

Lower heat to medium-low, and begin stirring mixture with a wooden spoon. Stir and cook until quite thick, 20-30 minutes, then add corn kernels and stir in. Add butter and stir in.

Cook, stirring very often, until kernels are cooked and the mixture thickens again, about 20 minutes.

Remove from heat and cool 10 minutes.

Place four 18-by-12 inch pieces of parchment on a work surface. Place a scoop of polenta in the middle, followed by green chilies, and cheese. Place another scoop of polenta on top, and fold parchment around to enclose the mixture. Place on a baking sheet, folded side down, and refrigerate.

To cook, place a wire rack in a large skillet along with 1/2 inch water and bring to a boil. Place packages on the rack, cover, lower heat, and steam for 30 minutes.

Unwrap and serve.