For years, our classic way of preparing a butterflied leg of lamb has been wonderfully straightforward: fresh herbs, Dijon mustard, garlic, good olive oil—and a hot grill.
It is one of those dependable dishes that feels both rustic and elegant. The mustard sharpens the richness of the lamb. The herbs perfume it. The grill supplies the smoke, char and crisp little edges that everyone reaches for first.
But a butterflied leg is rarely the same thickness from one end to the other. The thinner portions can become well done while we wait for the thickest section to reach its proper temperature. It was always a slog trying to get each piece adequately cooked.
And so, after resisting yet another kitchen device for as long as we reasonably could, we have finally climbed aboard the sous-vide bandwagon.
We are rather pleased that we did.
Sous vide does not replace the grill. It simply gives us much greater control over what happens before the lamb reaches the fire.
My recommendation for the home cook is the compact Anova Precision® Cooker Mini. It clips onto an ordinary cooking vessel and circulates water at a precisely controlled temperature. It is small, approachable and powerful enough for everyday home cooking. In other words, it is a very sensible way to enter the world of sous vide without turning the kitchen into a laboratory. But what really grabbed us is the wifi app which ensures precision cooking down to 1 degree!
What follows is our classic herb-and-Dijon lamb—with two paths to the grill:
The new sous-vide method, for exceptional control and wonderfully even doneness.
The more traditional reverse-sear method, for those who are not yet ready to purchase a precision cooker.
Both paths end in the same place: over a lively grill, where the lamb develops its savory crust and unmistakable summer character.
Butterflied Leg of Lamb with Herbs and Dijon
Serves 6–8
For the lamb
One 4- to 5-pound boneless, butterflied leg of lamb
Kosher salt
Freshly ground black pepper
Olive oil for preparing the meat and grill
For the herb-and-Dijon paste
1/3 cup Dijon mustard
2 tablespoons extra-virgin olive oil
2 tablespoons finely chopped fresh rosemary
2 tablespoons fresh thyme leaves
1 tablespoon finely chopped fresh oregano or marjoram
2 tablespoons chopped flat-leaf parsley
1 tablespoon lemon zest
1 tablespoon fresh lemon juice
1 teaspoon garlic powder for the sous-vide bag—or 3 finely minced garlic cloves for the reverse-sear version
1 tablespoon of kosher salt
1/2 teaspoon freshly ground black pepper
The exact mixture of herbs is forgiving. Rosemary and thyme provide the backbone, but this is also a lovely place for oregano, marjoram, savory, parsley or a little mint from the garden.
Prepare the lamb
Open the butterflied lamb on a cutting board. Trim away any unusually thick pieces of surface fat or silver skin, but leave enough fat to baste and flavor the meat.
If one section is dramatically thicker than the others, make a shallow horizontal cut and open it like a book. The goal is not perfect uniformity. A little variation lets us offer both pinker and more fully cooked slices at the table.
Pat the lamb dry. Season both sides with salt and pepper.
Mix the Dijon, olive oil, herbs, lemon zest, lemon juice, garlic and seasonings into a thick paste. Spread it generously over both sides of the lamb, working it into all the folds and crevices.
Now choose your course.
THE SOUS-VIDE SIDEBAR
What exactly is sous vide?
Sous vide means “under vacuum.” Food is placed in a sealed bag and cooked in a temperature-controlled water bath.
The great advantage is simple: the lamb cannot become hotter than the water surrounding it. If the bath is set to 133°F, the meat gradually reaches 133°F from edge to edge. We are no longer trying to pull it from a hot oven during a narrow window before it overcooks.
Sous vide provides the interior doneness. It does not produce browning, smoke or a crust. That is why we still finish our lamb quickly over a very hot grill.
My recommended starting device
The proper name is the Anova Precision® Cooker Mini. It is an 850-watt compact immersion circulator designed for smaller home-cooking jobs. It attaches to a suitable pot or heat-safe container and is controlled through Bluetooth. See the Anova Precision Cooker Mini.
You will also need:
A deep pot or heat-safe container
A sturdy freezer-grade zipper bag or vacuum-sealing bag
A binder clip or sous-vide clip
A rack, plate or other food-safe weight if the bag tries to float
A vacuum sealer is helpful, but it is not mandatory. With a zipper bag, slowly lower the filled bag into the water while keeping its open edge above the surface. The water pressure pushes most of the air out. Seal the bag just before the opening reaches the water.
Choosing the lamb temperature
131–133°F: Rosy medium-rare
135–137°F: Medium-rare moving toward medium
139°F: Medium, with less visible pink
Anova advises against cooking leg of lamb below 130°F when it requires more than 2½ hours. Its published guidance gives a general cooking range of approximately 3½ to 12 hours. Read Anova’s leg-of-lamb guide.
For a butterflied leg, I recommend beginning at 133°F for approximately 6 hours. If your guests prefer lamb closer to medium, use 137–139°F.
Because fresh garlic can remain surprisingly sharp when cooked at sous-vide temperatures, I use garlic powder in the sealed bag. Fresh minced garlic can be incorporated into a small amount of reserved Dijon-herb paste and brushed onto the lamb immediately before grilling.
Course One: Sous Vide, Then Grill
Set the Anova Precision Cooker Mini to your chosen temperature. My starting point is 133°F.
Place the seasoned lamb in a vacuum bag or heavy-duty zipper bag. Arrange it as flatly as possible. Seal the bag and lower it into the preheated water bath, making certain the meat is submerged while the sealed opening remains safely above the water.
Cook for approximately 6 hours. A particularly thick leg can remain in the bath for 7 or 8 hours without the frantic timing demanded by a conventional roast.
Anova’s own butterflied-leg recipe uses 139°F for 6 to 8 hours, followed by a short grill finish. See Anova’s butterflied leg of lamb method.
Prepare for the grill
Preheat a gas or charcoal grill until it is very hot. Clean and lightly oil the grates.
Remove the lamb from its bag. Save the juices if you would like to use them in a sauce.
Now comes one of the most important sous-vide rules:
Pat the lamb extremely dry.
Moisture creates steam, and steam is the enemy of fast, flavorful browning. Use several paper towels and dry every surface and fold.
If desired, brush the lamb very lightly with a fresh mixture of Dijon, olive oil, herbs and minced garlic. Do not apply a heavy coating—the mustard can scorch before the meat develops its crust.
Place the lamb over direct high heat. Grill for approximately 2 to 4 minutes per side, moving and turning it as needed, until the exterior is deeply browned and lightly charred.
Remember that the lamb is already cooked. We are not trying to raise its internal temperature substantially. We are creating color, smoke, aroma and crust.
Transfer it to a cutting board and allow it to rest for about 5 minutes.
Course Two: Reverse Sear, Then Grill
A reverse sear follows the same basic logic as sous vide, but uses a low oven instead of a controlled water bath.
Traditional roasting exposes the exterior of the meat to high heat while we wait for the center to cook. A reverse sear begins gently. The lamb is brought close to its desired temperature in a low oven and then moved to a fiercely hot grill for its final crust.
This provides more even cooking and a wider margin for success than placing the raw lamb directly over a hot fire.
The reverse-sear method
Preheat the oven to 250°F.
Place the herb-and-Dijon-coated lamb on a wire rack set over a rimmed sheet pan. Insert a reliable probe thermometer into the thickest portion.
Roast until the thickest section reaches:
115–120°F for a medium-rare final result
123–125°F for a medium final result
Depending upon its thickness, the lamb may require approximately 45 to 90 minutes. Trust the thermometer rather than the clock.
While it roasts, heat the grill to high.
Remove the lamb from the oven and take it directly to the grill. Sear it over direct heat for approximately 3 to 5 minutes per side, turning as necessary, until a dark, aromatic crust has formed.
Watch the thinner sections carefully. They will finish first and can be moved to a cooler area of the grill while the thicker portions continue to brown.
Aim for a final temperature of approximately:
130–135°F for medium-rare
135–140°F for medium
Transfer the lamb to a board and let it rest for 10 to 15 minutes before carving.
Unlike the sous-vide version, the reverse-seared lamb needs a fuller rest because heat continues moving through the meat after it leaves the grill.
Carving and Serving
Look carefully at the grain of the meat. Because a butterflied leg contains several muscles, the direction of the grain may change from one section to another.
Separate the sections if necessary and slice each one thinly across the grain.
Arrange the lamb on a warm platter. Scatter it with parsley, thyme, mint or tender rosemary tips. Add lemon wedges and perhaps a final spoonful of good olive oil.
I especially like it served with:
Little roasted potatoes with rosemary
White beans with herbs and lemon
Grilled summer vegetables
A tomato, cucumber and feta salad
Buttered peas with mint
A cool yogurt, cucumber and herb sauce
Warm flatbread or a crusty country loaf
The thinner, more fully cooked pieces are usually claimed by guests who prefer less pink. The thicker rosy slices reward those of us who believe good lamb should still possess a blush.
The Real Advantage: More Time at the Table
Precision cooking sounds technical, but its best benefit is wonderfully human.
When friends arrive, I would rather pour a glass, walk through the garden and enjoy the conversation than repeatedly leave the gathering to poke and probe a roast.
Sous vide takes much of that anxiety away. The lamb can wait patiently in its bath until the grill is hot and the table is nearly ready. The final grilling becomes a brief bit of theater instead of a lengthy exercise in temperature management.
So yes—I have finally climbed aboard the bandwagon.
If you love lamb, herbs and summer cooking, I implore you to consider the Anova Precision Cooker Mini. Begin with a butterflied leg, give it the full rosemary-thyme-and-Dijon treatment, and let precision cooking handle the interior while your grill supplies the soul.
It is still my classic butterflied leg of lamb.
It has simply learned a very useful new trick.
Until next time...
I am...
Phil Wilson...
and Here’s to sharing our herbal life-style with you!