To make a rub, mix together the salt, pepper, brown sugar, granulated garlic, mustard powder, smoked paprika and chipotle chile powder. Taste and adjust seasonings. Sprinkle each slab of ribs evenly with the rub and then double wrap with foil, making note of which side is the bone side. Refrigerate the ribs for 2-8 hours. (They’re good after 2 hours but even better after 8.)
To bake, preheat the oven to 300° F and line two baking sheets with foil. Place the foil-wrapped ribs, bone side up, on the sheets, and cook for 1 hour and 30 minutes.
Meanwhile, in a saucepan stir together the brewed coffee, sorghum syrup, brown sugar, apple cider vinegar, Worcestershire sauce, garlic, chipotle chile powder and allspice. Cook on medium until the sugar has dissolved and then whisk in the mustard until well combined. (The mustard will probably break up a bit when you add it to the pot but a few turns of the whisk will incorporate it into the sauce.)
After 1 hour and 30 minutes, remove the ribs from the oven. Gently open the foil (a lot of steam will escape, so be careful) and take 1/4 cup of the meat juices and stir them into the sauce. Adjust seasonings and add salt to taste.
With tongs, remove the ribs from the foil and place back on the sheet, meat side up. Discard the foil that wrapped the ribs, as well as the remaining meat juices (unless you prefer to save the juices for another use).
Brush the meat side of the slabs with the sauce and return to the oven. Cook for 30 minutes uncovered and then brush each slab with the sauce again. Cook for 30 more minutes. Remove from the oven, turn on the broiler, brush each slab with sauce and then cook under the broiler for 1-3 minutes, or until darkened and dark spots appear.