In a small bowl, combine the dark brown sugar, paprika, chili powder, salt, garlic powder, onion powder, and dry mustard. Mix thoroughly until the brown sugar is evenly distributed throughout the spice blend, breaking up any clumps. This dry rub is the foundation of your flavor, so take a moment to ensure everything is well combined. Set aside until ready to use.

Pat the beef short ribs dry with paper towels, then generously coat all sides with the dry rub from Step 1, pressing gently so the spices adhere to the meat. Place the seasoned ribs in a large dish or on a baking sheet, cover loosely with plastic wrap, and let them rest at room temperature for 30 to 60 minutes. I find this resting period allows the seasonings to penetrate the meat and develop deeper flavor. While the ribs rest, preheat your grill to 375°F to 400°F.

Tear off four large sheets of heavy-duty foil (about 18 inches each). Divide the seasoned ribs equally among the four sheets, placing them in the center of each foil sheet, then top each portion with 2 ice cubes. Fold the foil edges up and seal tightly to create a packet that will trap steam during cooking. Place the sealed packets over indirect heat on your preheated grill (away from direct flame or hot coals) and cook for 1 1/2 to 2 hours, until the ribs are fork-tender. The ice cubes will melt slowly, creating steam that gently braises the meat while keeping it juicy.

Carefully open the foil packets (watch out for escaping steam!) and transfer the ribs to a plate, discarding the liquid. Place the ribs directly over medium-high heat on your grill. Generously coat all sides of each rib with barbecue sauce, then grill for about 5 minutes, turning once halfway through, until the sauce caramelizes and develops a nice char. I like to apply the sauce in thin layers rather than one thick coat—this creates a better glaze and prevents burning.

Transfer the glazed short ribs to a serving platter and let them rest for a few minutes. Serve immediately with extra barbecue sauce on the side for dipping or drizzling.