Preparation

Smoke the ribs

• Heat a smoker or grill to 225°F. Add applewood or cherrywood chips to the smoker per the manufacturer’s instructions.
• Loosen the membrane at the back of the ribs by slipping a butter knife between the rib bone and membrane to loosen the corner. Then, using a paper towel to grip the edge, pull the membrane away and discard.
• In a medium bowl, combine the sugar, paprika, salt, chili powder, onion powder, garlic powder, dried ginger, pepper, cumin, and cayenne. (Use immediately, or store in an airtight container at room temperature for up to 2 months.) Coat the ribs generously on both sides with the rub. Let the ribs sit at room temperature to allow the meat to sweat into the rub and form a paste, 10 to 15 minutes.
• Put the ribs in the smoker bone side down, and smoke according to the smoker manufacturer’s instructions for 3 hours.

Make the sauce

• Meanwhile, in a medium bowl, whisk the barbecue sauce, soy sauce, and ginger. Divide the sauce into two equal portions, reserving half for serving and half for basting.
• After the first 3 hours of smoking, lay each rack on 2 separate sheets of butcher’s paper or two sheets of foil large enough to encase the racks (doubling up prevents punctures and helps keep in the juices). Brush each rack on both sides with some of the sauce, and scatter 1 Tbs. of the butter on top of each rack. Wrap up and seal each parcel tightly, and then return the racks to the smoker for another 2 hours.
• Gently unwrap the ribs (there will be lots of liquid in the packages) to expose the top side of the meat. Brush the tops of the racks again with the sauce, divide the remaining 2 Tbs. of butter between them, and then return to the smoker for a final 15 minutes to set the sauce.
• Remove the ribs from the smoker. Garnish with the sesame seeds, and serve immediately with the reserved sauce.