This companion rub to the Sweet & Sassy Bourbon Barbecue Sauce is step one in making “Next Level Barbecue Chicken.” The secret is coating the chicken pieces in the rub and letting them grill over indirect heat without turning them, until they are almost done and the rub has created a nice crust on the skin. When you have about 7 minutes left, brush the chicken pieces with the sauce and let it set. The skin will be nice and crisp and the flavor of the rub and the sauce creates layers of flavor that make this next level. I grill whole portobello mushroom caps at the same time, seasoned with the rub and sauced for about 7 minutes. If doing this, let the chicken cook for about 20 minutes before adding the mushrooms to the cooking grates as they take half the time.
In a large saucepan on the stove, add tomatoes, sugar, molasses, Bourbon, ketchup, chili sauce, vinegars, and Worcestershire sauce, stirring after each additional ingredient to combine. Add the Classic Spice Rub and simmer until flavors have blended and sauce has thickened somewhat, about 30 minutes.
Let the sauce cool for about 10 minutes or until it is warm but no longer "boiling" hot. Puree using an immersion or traditional blender. Taste and adjust seasoning with salt, about 1/2 teaspoon, and freshly ground pepper. Remember, the meat will have plenty of spice rub on them, so don't over-season the sauce.
Add the cocoa powder and mix well to combine. Let sit 5 minutes and stir again to make sure cocoa powder is well distributed. Let cool and pour into a clean glass jar for storing. The sauce can be made in advance and kept for 2 weeks in the refrigerator.