Preheat oven to 350°F (175°C).

In a skillet, brown ground beef and chopped onions over medium heat.

Drain off any excess grease.

In the same skillet, stir in the drained green chilies, pork and beans, taco seasoning mix, and water.

Mix well to combine all ingredients.

Spread the bean mixture evenly into an 8-inch glass baking dish.

In a separate bowl, combine cornmeal, flour, baking powder, sugar, and salt.

Add shredded Cheddar cheese, milk, egg, and vegetable oil.

Mix until just combined; do not overmix.

Pour the cornbread batter evenly over the bean mixture in the baking dish.

Bake in the preheated oven for 35-40 minutes, or until the cornbread topping is golden brown and a toothpick inserted into the center comes out clean.

Let cool slightly before serving.