1. For the Rub: Combine mustard, ketchup, and garlic in small bowl; combine pepper, paprika, chili powder, cayenne, salt, and sugar in separate small bowl. Spread mustard mixture in thin, even layer over both sides of ribs; coat both sides with spice mixture, then wrap ribs in plastic and refrigerate for at least 8 hours and up to 24 hours.

2. Transfer ribs from refrigerator to freezer for 45 minutes. Adjust one oven rack to lowest position and second rack to upper-middle position (at least 5 inches below broiler). Place baking stone on lower rack; heat oven to 500°F. Sprinkle ground tea evenly over bottom of rimmed baking sheet; set wire rack on sheet. Place ribs meat side up on rack and cover with heavy-duty foil, crimping edges tightly to seal. Roast ribs directly on stone for 30 minutes, then reduce oven temperature to 250°F, leaving oven door open for 1 minute to cool. While oven is open, carefully open one corner of foil and pour apple juice into bottom of baking sheet; reseal foil. Continue to roast until meat is very tender and begins to pull away from bones, about 1 1/2 hours. (Begin to check ribs after 1 hour; leave loosely covered with foil for remaining cooking time.)

3. Remove foil and carefully flip racks bone side up; place baking sheet on upper-middle oven rack. Turn on broiler; cook ribs until well browned and crispy in spots, 5 to 10 minutes. Flip ribs meat side up and cook until well browned and crispy, 5 to 7 minutes more. Cool for at least 10 minutes before cutting into individual ribs. Serve with barbecue sauce, if desired.

Serves 4