Gigot d'Agneau à la Boulangère — Leg of Lamb Baked on Potatoes

Ingredients

• 2–2.5 kg bone-in leg of lamb
• 12–15 slivers garlic, cut into thin slivers
• 1.5 kg waxy potatoes, Charlotte, Ratte, or Kipfler — sliced 3 mm on a mandoline
• 3 large onions, thinly sliced
• 400 ml lamb or chicken stock, hot
• 1 tsp herbes de Provence
• 4 sprigs fresh thyme
• 2 bay leaves
• to season fine sea salt
• to season black pepper, freshly ground

Method

1. 1
   Using a paring knife, make 12–15 small incisions 2 cm deep all over the leg of lamb. Push one garlic sliver into each incision so it is fully embedded in the flesh. Season the lamb aggressively on all surfaces with salt, pepper, and herbes de Provence. The garlic is hidden inside the meat; it will perfume from within rather than burn at the surface.
2. 2
   Slice the waxy potatoes to exactly 3 mm on a mandoline. Slice the onions thinly by hand. Layer the potatoes and onions in a large, deep roasting dish with the thyme and bay leaves, seasoning the layers with salt and pepper as you build them. Pour the hot stock over the assembled bed; the liquid should reach just below the surface of the top potato layer — fully submerged potatoes will steam without crisping, while potatoes that stand above the stock will char before cooking through. This is the step on which the dish lives or dies.
3. 3
   Set the leg of lamb directly on top of the potato bed, bone side down. Place the dish in an oven preheated to 220 °C and roast uncovered for 20 minutes, until the lamb surface colours to a deep golden brown.
4. 4
   Reduce the oven to 180 °C and continue roasting for 60–70 minutes (calculate 25 minutes per 500 g). The lamb drippings fall continuously into the potatoes below. The leg is done at rosé when an instant-read thermometer reads 55–58 °C at the thickest part of the leg, away from the bone.
5. 5
   Transfer the lamb to a board and rest it uncovered for 20 minutes. During this time the potato dish goes back into the oven, now raised to 220 °C, for 10 minutes. The top layer of potatoes should emerge golden and beginning to crisp at the edges, while the layers beneath remain creamy and saturated with lamb-flavoured stock. Remove when the surface is visibly golden and the edges show a light crust.
6. 6
   Carve the leg at the table into thick slices. Serve with generous spoonfuls of the boulangère potatoes, ensuring each portion draws from both the crisp top layer and the tender, stock-laden layers below. The potatoes should smell richly of meat and thyme.