One approximately 4–5-pound boneless leg of lamb coated with Julia Child's Dijon-soy herbal mustard mixture, vacuum-sealed, cooked sous vide using Kenji López-Alt's 130°F baseline, and reverse-seared.
Prepare & package
Remove and reserve the leg bone for Lamb Stew stock if starting with a bone-in leg. Combine Dijon mustard, soy sauce, garlic, ground rosemary or thyme, powdered ginger, and olive oil into a creamy coating. Coat the lamb several hours ahead if practical, vacuum-seal, and refrigerate or freeze.
Store & thaw
Keep refrigerated for near-term cooking or freeze vacuum-sealed. Thaw fully in the refrigerator before using the two-hour sous-vide schedule.
Cook or reheat
Sous vide the thawed, approximately 4–5-pound butterflied boneless leg at 130°F for 2 hours.
Finish & serve
Remove from the bag and pat thoroughly dry. Sear over very high heat, turning to brown all sides, for approximately four minutes total. Slice for serving. Reserve the bone for stock and use substantial cooked leftovers in Leftover American Lamb Stew.