This recipe requires an accurate thermometer, as well as a picnic cooler capable of holding at least 2 gallons of liquid with a tight-fitting lid. Some coolers retain heat better than others. Heat retention can be further improved by draping several towels over the cooler during step 2. Leaving the cooler in a warm spot helps—I leave mine either in direct sunlight on a warm day, or in a warm corner of the kitchen indoors. Lamb racks can be left in cooler for up to 3 hours before searing or grilling.
I prefer leaving extra fat and breast meat attached to the ribs for gnawing and bone-sucking but if desired it can be removed following our instructions on frenching here. Make sure you buy lamb racks with the chine bone removed to make it easier to cut between chops after cooking. Most pre-packaged lamb will already have the chine bone removed. If buying lamb from the butcher's case, ask your butcher to do it for you—it's impossible to do at home without a hacksaw.
- 2 lamb racks with 8 ribs each (3 to 4 pounds total)
- Kosher salt and freshly cracked black pepper
- 8 sprigs rosemary or thyme (optional)
- 2 medium shallots, roughly chopped (optional)
- 4 medium cloves garlic, roughly chopped (optional)
- 1 tablespoon vegetable oil
Season lamb generously with salt and pepper on all sides. Place inside two gallon-sized zipper lock bags along with optional aromatics (for particularly large racks, split into 4 four-rib sections and use more bags as necessary). Squeeze out as much air from bags as possible with hands and close zipper lock, leaving one-inch un-sealed. Slowly submerge lamb in large pot of water, until only sealing edge of bags is exposed. Any remaining air should be forced out of bag as it is submerged. Seal bag completely. Repeat with remaining bags, then set all bags aside.
Heat at least two gallons of water on the stovetops to 130 degrees for medium rare or 145 degrees for medium, using instant-read thermometer to ensure temperature accuracy (in some homes, the hot tap may be hot enough without having to use the stovetop). Pour water into picnic-size chest cooler. Add water until cooler is filled with water at desired temperature, sealing cooler in between additions in order to retain heat. Add lamb to cooler, seal, and set it warm spot for at least 45 minutes, and up to three hours, checking temperature of water after 15 minutes to ensure that it isn't losing heat too rapidly (water should lose at most 1 degree of temperature after 15 minutes—if it has lost more, top up with boiling water, and drape cooler with several bath towels to help insulate.
Remove lamb racks from bags, discard aromatics (if using), and pat dry with paper towels. Heat oil in heavy-bottomed 12-inch stainless steel, cast iron, or non-stick skillet over high heat until lightly smoking. Add lamb to skillet fat-side down and sear until well-browned on all sides, turning with tongs as necessary, about 5 minutes total (for particularly large racks, sear lamb in two batches, tenting first batch with foil after searing to retain heat). Tent seared lamb with foil, allow to rest 5 minutes, carve, and serve.
Light large chimney starter 3/4 filled with charcoal (4 quarts, about 75 briquettes), and burn until coals are coated in thin layer of gray ash, about 20 minutes. Empty coals and spread evenly over half of grates. Position grill grates on top of grill, cover grill, and heat until grate is hot, about 5 minutes. Scrub grill clean with grill brush if necessary. Meanwhile, remove lamb racks from bags, discard aromatics (if using), and pat dry with paper towels. Rub lamb racks evenly with oil. Place racks, fat-side down over coals and grill until well browned on all sides, about 6 minutes total, moving lamb to cooler side of grill as necessary to avoid flare-ups. Remove lamb from grill, tent with foil, allow to rest 5 minutes, carve, and serve.
Beer cooler or sous-vide circulator