Gigot d’Agneau Boulangère (Leg of Lamb with Boulangère Potatoes)

Gigot d’agneau boulangère is a classic French-style roast that turns the joint and its side dish into one generous centrepiece. The leg of lamb roasts above thinly layered potatoes and onions, so the vegetables soften in lamb stock while catching the savoury juices from the meat. Garlic and rosemary give the lamb its recognisable aromatic depth, while the potatoes become tender underneath with a lightly bronzed, glossy surface. It is the kind of dish that suits Sunday lunch or a relaxed dinner for guests: substantial, neatly structured, and served straight from the roasting pan with the carved lamb.
Cuisine style French roast dinner
Flavor profile Savoury • Herby • Rich
Techniques Roasting • Baking • Resting
Key equipment Oven • Roasting pan • Chef’s knife
Time commitment Under 3 hours
Cooking style Crowd-friendly

Why this recipe works

  • Classic boulangère method: Roasting the lamb directly over sliced potatoes lets the stock, onions and meat juices combine into a deeply savoury base.
  • Aromatic seasoning: Garlic and rosemary are tucked into the lamb so their flavour perfumes the meat as it cooks rather than sitting only on the surface.
  • Main and side together: The potatoes cook underneath the joint, so the dish produces both carved roast lamb and a rich potato accompaniment in one pan.
  • Generous roast-dinner finish: Tender lamb, soft onions and stock-baked potatoes give the dish the satisfying, family-style character of a classic roast.

Get the most out of this recipe

Timing notes

  • Rest before carving: Let the lamb rest loosely covered before slicing; this helps the juices settle and gives cleaner, more tender slices.
  • Finish the potatoes while the lamb rests: Returning the potatoes to the oven after the lamb comes out reduces the stock and gives the top layer a more concentrated, glossy finish.

Ingredient notes

  • Choose a bone-in leg: A bone-in leg suits this style of roasting because it brings structure, flavour and a traditional presentation for carving.
  • Use good lamb stock: The stock becomes part of the potato dish, so a well-flavoured lamb stock makes a noticeable difference to the final savoury depth.
  • Slice the potatoes evenly: Even, thin potato slices cook at the same rate and absorb the stock more consistently.

Common mistakes

  • Do not flood the potatoes: The stock should come partway up the potato layers, not cover them completely, or the dish can turn soupy rather than glossy.
  • Watch the lamb, not just the clock: A meat thermometer is the most reliable guide, as leg size and oven performance can change the final cooking time.
  • Avoid carving straight away: Cutting the lamb as soon as it leaves the oven can release too much juice onto the board and make the meat seem drier.

Serving ideas

  • Add something green: Serve with simply cooked green beans, peas, spinach or a crisp bitter-leaf salad to balance the richness.
  • Keep the pan juices: Spoon the reduced juices from the roasting pan over the carved lamb and potatoes for extra savoury depth.

Equipment you'll need

Ingredients
Instructions
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  1. Heat the oven to 220°C (430°F). Pat the lamb dry, then rub all over with the olive oil, 1 tsp of the fine sea salt and the black pepper. Peel and thinly slice the garlic, then strip the rosemary leaves from the sprigs.
  2. With the tip of a knife, make small slits all over the lamb and push the garlic slices and rosemary leaves into them. Set the lamb on a plate while you prepare the potatoes. This brief stand helps the seasoning adhere.
  3. Peel and thinly slice the onions and potatoes. Dot the butter over the base of a roasting pan, then layer half the potatoes, all the onions, and the remaining potatoes, seasoning the layers with the remaining 1 tsp fine sea salt. Pour in the lamb stock; it should come partway up the potatoes, not cover them.
  4. Sit the lamb on top of the potatoes and roast for 20 minutes to start browning. Reduce the oven to 180°C (355°F) and continue roasting for 60 to 70 minutes, until the lamb is cooked to your liking and the potatoes are tender when pierced. If the potatoes look dry at any point, spoon a little stock from the pan over the top.
  5. Transfer the lamb to a board and rest for 15 minutes, loosely covered. Return the potatoes to the oven for 10 minutes to deepen the colour and reduce the stock to a glossy finish. Carve the lamb and serve with the boulangère potatoes and onions.

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Recipe notes

Tips

  • For neat slices, carve across the grain and keep the knife close to the bone as you work around the joint.
  • If you have a thermometer, aim for 55 to 60°C (130 to 140°F) for pink lamb, or 65°C (150°F) for medium.
  • If serving vulnerable groups, cook the lamb to at least 70°C (160°F) and ensure the juices run clear.

Substitutions

  • Replace Fresh rosemary with fresh thyme for a softer, more floral herb note.
  • Replace Butter with Extra virgin olive oil for a lighter finish (the potatoes will be less rich).

Storage

  • Refrigerate up to 3 days
  • Cool leftovers quickly, then refrigerate in a sealed container. Reheat lamb and potatoes in a 180°C (355°F) oven until piping hot; add a splash of Lamb stock to loosen the potatoes if needed. Freeze in portions for up to 2 months and defrost overnight in the fridge before reheating.

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Recipe overview

  • Servings: 4 servings
  • Total time: 2h 5min (30min active)
  • Difficulty: Medium
  • Cuisine: French
  • Allergens:
    Milk
One pot Freezer friendly Kid friendly

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