When ready to cook, preheat oven to 300° F. Line a rimmed sheet pan with aluminum foil and place a flat rack into the pan. Remove the lamb ribs from their bag, letting any excess marinade drip off. Discard any remaining marinade, except the garlic cloves, which you can place into the sheet pan.
The riblets are done when they register 145 F on an instant-read meat thermometer. Let the riblets rest for at least three minutes before serving. Braising lamb riblets in a flavorful liquid keeps them tender and moist. Start by browning the seasoned ribs in a little oil over medium heat.
Bake the ribs for 1 hour. Remove and discard the foil. Return the pan to the oven for 30 minutes. After 30 minutes, turn the racks over and return to the oven for another 30 minutes (the riblets will have now cooked for 2 hours). Check the meat for tenderness by pulling at the edge with a fork.
Because the flavor is rich and fatty, it's best to serve these ribs with something green or acidic. I served mine with steamed spinach tossed with a little olive oil and fresh lemon juice. A spicy cabbage or fennel cole slaw (see our recipe) would also be good. 3 pounds lamb riblets (this is about 2 racks) For the marinade: