Preheat oven to 400°F and grease a muffin pan.
Mix Jiffy cornbread mix, egg, and milk until just combined.
Fold in the cooked chicken, BBQ sauce, and ½ cup cheddar.
Divide evenly among 8 muffin cups and top with remaining cheese.
Bake for approximately 15 minutes, until golden and the centers are set. Let cool for 5 minutes.