Heat a tablespoon of olive oil in a large skillet over medium heat. Season chicken with salt and pepper, then sauté for 5-7 minutes until browned. Remove and keep warm.

In the same skillet, melt 2 tablespoons of butter and sauté diced onion for 3-5 minutes until translucent.

Add frozen vegetables to the skillet and cook for about 5 minutes until warmed through.

Sprinkle 2 tablespoons of flour over the veggie mixture and cook for 2 minutes. Whisk in 2 cups of chicken broth and 1 cup of milk. Stir until thickened.

Reintroduce chicken into the skillet and heat for 2-3 minutes until warmed and well combined.

Pour the filling into a greased 9x13-inch baking dish, then prepare the cornbread mix and spread over the filling.

Preheat the oven to 400°F (200°C) and bake for 22-26 minutes until the cornbread topping is golden brown.

Let cool for about 5 minutes before serving.