Preheat oven to 375 degrees.: The warm, preheated oven is crucial for even baking, producing a golden top and heated filling without overcooking. You should feel a gentle oven hum and see the temperature stabilize before the casserole goes in. A common mistake is not preheating, which can lead to uneven rise and a soggy center. If your oven runs hot, use an oven thermometer to confirm accuracy.
In a large skillet, add ground chicken and cook over medium heat, while breaking up chicken into small pieces. Cook until chicken is cooked through, about 10 minutes. Drain excess fat and add chicken to a 13" x 9" casserole dish. Add the remaining ingredients to the casserole dish (except cornbread topping), stir well. Make sure the mixture is evenly distributed.: As the chicken hits the skillet you will hear a steady sizzle and see the meat change from pink to pale and then to lightly browned, releasing savory juices. Browning creates flavor through the Maillard reaction, which deepens the overall taste when combined with salsa. Avoid overcrowding the pan; too much meat at once will steam instead of brown. If excess moisture accumulates, drain it so the filling stays saucy not watery.
In a medium bowl, combine cornmeal, baking powder, soda and salt. Add egg and buttermilk, stir just until combined. Spread batter evenly over the mixture, sprinkle with 1/4 cup cheese and bake until cornbread is golden and casserole is heated through, approximately 25-30 minutes.: Properly cooked chicken should no longer be pink and should reach a firm texture when stirred. The edges should show slight browning to indicate caramelization. Overcooking will dry it out, so watch for a tender, slightly springy feel. Use a spatula to break the meat into small, consistent pieces so each bite has balanced texture.
Drain excess fat and add chicken to a 13" x 9" casserole dish.: Draining removes excess grease that could make the casserole heavy, while transferring the chicken to the dish begins the assembly phase. The casserole dish should be large enough for even layering, and you will smell the concentrated meat aroma as the liquid is removed. A mistake is leaving too much fat, which can make the top soggy; drain thoroughly but quickly so you keep the flavorful browned bits.
Add the remaining ingredients to the casserole dish (except cornbread topping), stir well.: When you fold in the jarred chipotle salsa , canned black beans , diced green chiles, spices, and shredded cheese , the mixture should look cohesive and saucy but not soupy. You will see flecks of cilantro and dark beans distributed through the mixture. Stirring evenly ensures every bite has balance; failing to mix thoroughly can leave pockets that are overly saucy or bland.
Make sure the mixture is evenly distributed.: Use a spatula to spread the filling so it covers the base in an even layer, which promotes uniform baking and heating. Visually, the surface should be level, and you should feel a slight resistance when running the spatula across it. If the filling is piled, the cornmeal topping may bake unevenly. Smooth out bumps for best results.
In a medium bowl, combine cornmeal, baking powder, soda and salt.: Dry mixing aerates the cornmeal and ensures the leavening agents are evenly dispersed, which is key for a consistent crumb in the topping. You will see a uniform pale mixture, and the texture should be slightly sandy. Skipping thorough mixing risks uneven pockets of baking soda or powder, which causes irregular rise and flavor.
Add egg and buttermilk, stir just until combined.: When you add the whipped egg and buttermilk , the batter will become moistened and slightly thick. Stir gently until there are no large dry patches, keeping some small lumps is fine. Overmixing develops structure and can yield a tougher top, so stop when the ingredients are homogenous. A common pitfall is vigorous mixing, which ruins the tender crumb you want.
Spread batter evenly over the mixture, sprinkle with 1/4 cup cheese and bake until cornbread is golden and casserole is heated through, approximately 25 to 30 minutes.: As the casserole bakes you will smell a toasty, slightly sweet corn aroma and the top will turn a warm golden color with bubbling edges. The cheese on top should melt and brown slightly, creating visual contrast. Test doneness by inserting a toothpick into the topping, it should come out mostly clean with a few moist crumbs. Avoid opening the oven frequently, which releases heat and prolongs baking. If the top browns too quickly, tent with foil to let the center finish cooking without burning the crust.