Spicy and Sticky Baby Back Ribs

INGREDIENTS:

1. 1 cup dark brown sugar
2. 3 tablespoons kosher salt
3. 1 tablespoon dry mustard
4. 1 tablespoon ground fennel
5. 1 tablespoon freshly ground black pepper
6. 1 tablespoon cayenne pepper
7. 1 tablespoon sweet smoked paprika
8. 4 racks baby back ribs (about 2 1/2 pounds each), membrane removed from the underside of each rack
9. 1 tablespoon unsalted butter
10. 1 small onion, minced
11. 3 garlic cloves, minced
12. 1 1/2 teaspoons dried thyme
13. 1 cup ketchup
14. 1 cup cider vinegar
15. 1 cup beef broth
16. 1/4 cup hot sauce
17. 1/4 cup Worcestershire sauce
18. 2 tablespoons unsulfured molasses

DIRECTIONS:

1. In a small bowl, combine the brown sugar, salt, mustard, fennel, black pepper, cayenne and paprika. On 2 large rimmed baking sheets, sprinkle the spice mix all over the ribs, pressing and patting it. Cover with foil and refrigerate overnight.
2. Preheat the oven to 250°. Pour off any liquid on the baking sheets, cover the ribs with foil and roast for about 3 hours, until the meat is tender but not falling off the bone. Pour off any liquid on the baking sheets.
3. Meanwhile, in a saucepan, melt the butter. Add the onion, garlic and thyme and cook over moderate heat until the onion is softened, about 5 minutes. Add the ketchup, vinegar, beef broth, hot sauce, Worcestershire sauce and molasses and bring to a boil. Simmer over low heat, stirring occasionally, until thickened, about 30 minutes.
4. Preheat the broiler and position a rack 10 inches from the heat. Brush the ribs liberally with the barbecue sauce and broil for about 10 minutes, turning and brushing occasionally with the sauce, until well-browned and crispy in spots. Transfer the ribs to a work surface and let rest for 5 minutes. Cut in between the bones and mound the ribs on a platter. Pass any extra barbecue sauce on the side.

MAKE AHEAD The roasted ribs and barbecue sauce can be refrigerated separately for up to 4 days. Return to room temperature and broil just before serving.