How to Make It
Preheat oven to 425°F. Heat a large cast-iron skillet over medium-high. Add beef and onion; cook, stirring often, until meat is browned and onion is translucent, about 10 minutes. Add chile powder and cumin, and cook, stirring constantly until fragrant, about 1 minute. Stir in tomato sauce, broth, corn, beans, green chiles, and salt. Bring to a boil; reduce heat to medium to maintain a simmer. Simmer until thickened, about 10 minutes.
Meanwhile, stir together crushed chips, cornmeal, sugar, baking powder, and pepper in a medium bowl. In a separate bowl, whisk together egg and 1/3 cup of the milk. Pour milk mixture into cornmeal mixture, and stir to incorporate. Fold in cheese and butter. (If too thick, stir in remaining milk.)
Spread cornbread mixture evenly over chili mixture. Bake in preheated oven until cornbread is browned and cooked through, about 15 minutes. Let stand 5 to 10 minutes before serving. Garnish with desired toppings.