Preheat the oven to 375°F. Spray an 8x8-inch glass baking dish with cooking spray.

For the Chili: Set a large skillet over medium-high heat and add the oil. When the oil is hot, add onion and cook for 3 minutes, until softened.  Add the black beans, kidney beans, garlic salt, tomato sauce, pico de gallo salsa, chili seasoning mix, and black pepper. Mix well, reduce heat to low and simmer for 20 minutes, allowing the flavors to meld. Adjust seasoning to taste and serve hot.

For the Cornbread Layer: Set a medium saucepan over medium heat. Add the broth, milk, and cornmeal, whisk to combine. Bring to a boil, whisking frequently. Reduce heat to low and simmer, whisking occasionally, until thick and smooth, about 3 minutes. Remove from the heat and stir in the butter.

Spoon 1/3 of the cornbread mixture evenly over the bottom of the prepared casserole dish. then top with the warm chili. Sprinkle the corn over the top of the chili, then gently spread the remaining cornbread batter in an even layer over the chili and sprinkle with the shredded cheese.

Bake in the preheated oven for 30 minutes, until the chili bubbles around the edges of the cornbread and the top is golden. Divide into individual portions and serve hot.