Sous Vide Rack of Lamb with Lemon Thyme and Garlic

Rack of lamb is expensive, lean, and not particularly forgiving. Traditional roasting gives you a very small margin for error and often results in the classic bullseye: rare in the center, gray and overcooked by the edges. Sous vide removes that risk almost entirely.

Cooking the lamb in a temperature-controlled water bath lets you decide the final doneness up front and achieve that doneness evenly from edge to center. Timing becomes flexible instead of stressful, moisture stays locked in, and the final sear is about flavor and texture, not damage control. It is an especially good approach when cooking for guests, because the work is cleanly split into two phases: precise, hands-off cooking ahead of time, followed by a fast, dramatic finish right before serving.

This recipe is written for two frenched racks of lamb, each with eight bones, and comfortably serves four people. Plan on three to four rib chops per person, which is a generous main-course portion when served with sides.

Snapshot

• Implements: sous vide circulator; large container for water bath; ping pong balls or lid to reduce evaporation; vacuum sealer and bags; heavy skillet (preferably cast iron); paper towels
• Cooker setting: 130°F (54.5°C) for 2.5 to 3 hours (thawed) or 3.5 to 4 hours (frozen)
• Batch size: 2 frenched racks of lamb, about 1.5 to 1.7 lb each, serving 4

Ingredients

For the lamb

• 2 frenched racks of lamb, about 1.5 to 1.7 lb each
• Kosher salt
• Freshly ground black pepper (optional)

For each vacuum bag

• 1 smashed garlic clove
• 1 small sprig lemon thyme

For searing

• Neutral high-heat oil or duck fat

Optional finishing baste

• 1 to 2 Tbsp butter per rack
• 1 lightly crushed garlic clove
• 1 fresh sprig lemon thyme

Method

1. Season and bag.

   Remove any silverskin from the concave side of the racks, but do not trim the fat. Pat the lamb racks dry.

   Season on all sides with kosher salt. Lamb benefits from assertive salting. Add black pepper if you like, but keep it restrained.

   Place each rack in its own vacuum bag. Add to each bag on the meat side (not the fat cap):

   • 1 smashed garlic clove
   • 1 small sprig lemon thyme

   Do not add butter, oil, or other fat to the bag. In a sealed sous vide environment, fats pull flavor out of the meat instead of basting it.

   Vacuum seal snugly so the aromatics stay in contact with the lamb.

2. Sous vide cooking.

   Preheat the water bath to 130°F (54.5°C) for medium rare.

   Cooking time depends on starting temperature:

   • Fully thawed: 2.5 to 3 hours
   • Partially thawed (cold center, firm): 3 to 3.5 hours
   • Fully frozen: 3.5 to 4 hours

   Submerge the bags fully. Frozen racks may float at first, so clip or weight them until they thaw. Ping pong balls on the surface help reduce evaporation and improve temperature stability.

   The lamb can safely hold at temperature for up to 4 to 5 hours total without overcooking, which makes this ideal for entertaining.

3. Remove and dry.

   Remove the racks from the bags and discard the aromatics.

   Pat the lamb extremely dry with paper towels. This step is critical. Moisture is the enemy of browning.

   For best results, let the racks rest uncovered in the refrigerator for 10 to 20 minutes to further dry the surface before searing.

4. Sear hard and fast.

   Heat a heavy skillet over high heat until very hot.

   Add a thin film of neutral oil or duck fat.

   Place the rack fat-side down first and press gently so the fat cap makes full contact with the pan. Sear for 45 to 60 seconds until deeply browned.

   Sear the remaining sides briefly, about 20 to 30 seconds per side. You are developing crust, not cooking the interior.

   Optional butter baste:

   • Lower heat slightly
   • Add butter, garlic, and lemon thyme
   • Baste for 20 to 30 seconds
   • Remove promptly to avoid over-browning

5. Rest and slice.

   Let the racks rest for 5 minutes.

   Slice cleanly between the bones and serve immediately.

Notes, swaps, and guardrails

Why sous vide for rack of lamb

Rack of lamb is expensive, lean, and unforgiving. Traditional roasting leaves very little margin for error and often produces a bullseye effect, rare in the center and gray at the edges. Sous vide removes that risk entirely. By cooking the lamb in a temperature-controlled water bath, you choose the final doneness in advance and get that doneness from edge to center. Timing becomes flexible, juiciness is preserved, and the final sear becomes purely about flavor and texture instead of internal temperature.

Why no fat in the bag

Do not add butter, oil, or duck fat to the bag. In a sealed sous vide environment, fats pull flavor out of the meat instead of basting it. Save the butter and duck fat for the pan, where they belong.

Lemon thyme and garlic notes

Lemon thyme provides gentle brightness without overpowering the lamb. Do not pair it with lemon peel in the bag. Garlic should be smashed, not minced, to avoid harsh sulfur flavors.

If you do not have lemon thyme, you can substitute (place on the meat side, not the fat cap):

• ¼ Tsp freeze-dried thyme, lightly crushed
• One thin strip of lemon zest, about 1 × ½ inch. Yellow only, no white pith

One rack per bag

One rack per vacuum bag ensures even cooking and easy handling. This method scales easily. Just add more bags and maintain water circulation.

Timing: cooking from frozen vs thawed

Sous vide cooking time depends less on weight and more on starting temperature. A rack of lamb that is fully thawed heats up faster than one that is partially or fully frozen, even if they weigh the same.

Use these timing guidelines at 130°F (54.5°C):

• Fully thawed: 2.5 to 3 hours
• Partially thawed (cold center, firm): 3 to 3.5 hours
• Fully frozen: 3.5 to 4 hours

The extra time accounts for thawing and heat-up, not additional cooking. Once the lamb reaches the bath temperature, it will not overcook or dry out, even if held for an extra hour.

If you are unsure which category your lamb falls into, err on the longer time. Sous vide at this temperature is very forgiving, and flexibility is one of its biggest advantages.

The drying step matters

Patting the lamb extremely dry after removing it from the bag is critical. Moisture is the enemy of browning. For best results, let the racks rest uncovered in the refrigerator for 10 to 20 minutes to further dry the surface before searing.

Make-ahead friendly

You can sous vide the lamb up to a day ahead, chill the sealed bags in an ice bath, and refrigerate. Rewarm in a 130°F (54.5°C) bath for 30 to 45 minutes, then sear just before serving.

What to expect

• Perfectly even medium rare from edge to center
• Juicy, tender meat with no gray band
• Subtle herbal and citrus aroma that complements rather than masks the lamb
• Restaurant-level consistency with minimal stress

Credit where it’s due

This recipe follows what I learned from Kenji’s sous vide lamb technique on Serious Eats, adjusted to my preferred flavors.