Combine cornmeal mix and sugar in a medium bowl; make a well in center of mixture.
Stir together buttermilk and egg; add to cornmeal mixture, stirring just until dry ingredients are moistened. Stir in melted butter, cheese, and chopped green chiles. Remove pan from oven, and coat with cooking spray. Spoon batter into hot muffin pan, filling almost completely full.
Bake at 425° for 15 to 20 minutes or until golden. Remove from pan to a wire rack, and let cool 10 minutes.