PREHEAT oven to 350ºF. Prepare corn bread mix as directed on package. Stir in 1/2 cup of the corn and the cheese. Pour into lightly greased 8-inch square baking pan. Bake 20 min.
MEANWHILE, heat oil in large skillet on medium heat. Add onions; cook 4 to 5 min. or until softened. Stir in poblano chiles and remaining corn. Cook 5 min. or until heated through. Stir in sour cream, water and salt; cook 3 min. or until heated through.
CUT corn bread into 12 equal squares; top evenly with poblano mixture. Serve immediately.