The sauce in this recipe has always been our "mother" competition sauce--the base we use to make the sauces we serve for competition judges. It is very forgiving for tweaking, so use it as a palette with which to add your favorite flavors. One of my favorite variations is to add a cup of peach or mango puree to 2 cups of the sauce for a fresh taste. When cooking competition chicken, I leave out the diced onion and substitute 1 tablespoon of onion powder, as I like a smoother finish on chicken.
For the basic BBQ rub: Using a coffee grinder, grind the turbinado sugar with a few "pulses" until it is lightly powdered. Combine with the granulated sugar, salt, onion powder, granulated garlic, cayenne, black pepper, mustard, chili powder, cumin and paprika in a bowl and hand stir until well incorporated. Store in an airtight container.
For the BBQ mother sauce: In a medium saucepan, heat the oil over medium heat. Add the onion and saute until translucent, about 5 minutes. Turn the heat to low if the onion is cooking too fast--you don't want it caramelized or browned. As the onion is getting close, add the garlic and cook until lightly golden, about 2 minutes longer. Add the ketchup, honey, tomato paste, vinegar, brown sugar, Worcestershire, dry mustard, cayenne and black pepper and stir well. Slowly add up to 1/2 cup water until the sauce reaches the consistency you like. A slightly thick consistency is best. Add about 3 tablespoons of the basic BBQ rub, stir well and taste. The sauce should have a good, well-rounded flavor. Add more of the basic BBQ rub in 1-tablespoon increments until your desired flavor is achieved, up to about 1/2 cup total. Cool and store in an airtight container in the refrigerator for up to 10 days.
For the ribs: Rinse the ribs and remove the membrane from the back. Trim any excess fat from the tops of the slabs. Trim 1 bone from the large end of the ribs and 2 bones from the small end. This will give you a much more consistent slab for cooking.
Starting on the backs, sprinkle the slabs of ribs with approximately 1/2 tablespoon of the basic BBQ rub each, then add 1/2 tablespoon yellow mustard each and massage into the meat. Flip the ribs over and repeat. Wrap tightly with plastic wrap and refrigerate for at least 8 hours. For a contest, I marinate ribs like this for 12 to 16 hours.
Prepare a smoker to run at 225 degrees F with around 4 chunks of apple wood and 4 chunks of cherry wood so that the wood will smolder throughout the cooking. Remove the ribs from the refrigerator, unwrap and repeat the basic BBQ rub and mustard procedure, massaging them in. Don't get it too thick or paste-like, as this will give you a dark appearance when cooked. Place the ribs in the smoker meat-side up and cook for 2 hours. Remove the ribs from the smoker and increase the temperature to 250 degrees F. Apply the basic BBQ rub and mustard to both sides of the ribs as before. On the top sides, slather approximately 1 tablespoon of honey over the surface of each slab, then sprinkle heavily with the turbinado sugar. Lay each slab of ribs meat-side up on a piece of heavy-duty aluminum foil and fold up the edges. Pour approximately 1 to 2 ounces of the grape juice into the bottom of each foil package, then finish wrapping the ribs but don't crimp the edges--you want steam to be able to escape.
Return the ribs to the cooker for 2 hours, then test for tenderness. (I cook ribs in this stage until they look overdone and too tender. Don't worry, they'll tighten up. If they still have too much texture, leave them in for 20 to 30 more minutes.) Remove the ribs from the cooker, open the foil and drain off the liquid. Using the foil as a tool, "roll" the ribs over so the bone side is up, glaze with the BBQ mother sauce, then roll them back over and glaze the tops. Using long tongs, carefully remove the ribs from the foil and place them back in the smoker for 15 minutes. This will let the glaze cook onto the ribs and let the ribs tighten back up. Remove from the cooker and allow to rest for 5 minutes, apply a very thin coat of sauce to "glisten" the ribs, then lightly sprinkle with chipotle powder before serving.