1. Prepare the barbecue for indirect cooking at very low heat 110 to 120°C.
2. In a medium-sized bowl, mix the rub ingredients. Place the spare-ribs, meaty side up, on a cutting board. Follow the line of fat that separates the meaty ribs from the much tougher tips at the base of each rack, and cut off the tips. Turn each rack over. Cut off the flap of meat attached in the center of each rack. Also cut off the flap of meat that hangs below the shorter end of the ribs. Using a blunt dinner knife, slide the tip under the membrane covering the back of each rack of ribs. Lift and loosen the membrane until it breaks, then grab a corner of it with a paper towel and pull it off. Season the spare-ribs all over with the rub, putting more of the rub on the meaty sides than on the bone sides.
3. In a small spray bottle, combine 175 ml apple juice and 60 ml cider vinegar.
4. Brush the cooking grate clean. Add two of the wood chunks to the charcoal. Smoke the spare-ribs, bone side down, over indirect very low heat, with the lid closed, until the meat has shrunk back from the bones by at least 1 cm, i.e. for 4 to 5 hours. After each hour, add more lit briquettes as necessary to maintain the heat, add one more wood chunk to the charcoal (until they have burned up), and spray the ribs on both sides with the apple juice mixture. Meanwhile, make the sauce.
5. Combine the sauce ingredients in a saucepan and bring to a simmer over medium heat. Reduce the heat to low, and cook for 15 to 20 minutes, stirring occasionally.
6. When the spare-ribs are done, remove them from the barbecue. Brush the racks on both sides with the sauce and wrap each rack in damp baking paper. Then wrap them in heavy-duty aluminum foil. Return the wrapped racks to the barbecue, stacking them on the cooking grate. Continue to cook over indirect very low heat, with the lid closed, until the meat is tender enough to tear with your fingers, i.e. for 45 minutes to 1 hour. Remove the spare-ribs from the barbecue and lightly brush the racks on both sides with sauce again. Return the marinated racks to the grill for another 15 minutes 110°C. Cut the racks into individual ribs. Serve warm with the remaining sauce on the side