Preheat oven to 350.

Pat chicken dry and lay on a piece of foil or a cutting board. Pull the skin back at least half-way and trim off with a pair of clean kitchen shears or scissors.

Combine rub spices and sprinkle over all sides of chicken, lightly patting in with clean hands. In a separate bowl, combine ketchup, brown sugar, honey, mustard, and Worcestershire sauce. Set aside.

Place a 12 inch cast iron skillet over medium heat. Add olive oil and tilt to cover bottom of pan. Arrange chicken pieces in pan and cook for 2-3 minutes on each side to sear. Remove chicken pieces and place back on your foil or cutting board.

Reduce heat to medium-low and add butter, onion, and garlic to pan. Cook for 1-2 minutes or just until softened. As it cooks, use a wooden spoon to scrape the browned bits from the chicken off the bottom of the pan.

Add ketchup mixture to pan and raise heat again to medium, stirring until sauce comes to a simmer. Turn heat off. Sprinkle in chocolate and stir to incorporate and melt.

Add chicken drumsticks back to pan, turning to coat each one in sauce and arrange in a single layer. Use potholders to transfer hot pan to oven and bake for 45 minutes. Internal temperature should reach at least 165 degrees.

Remove from oven and let cool for a few minutes before serving.