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Leg of Lamb Roasted Over Potato-Onion Gratin


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Rate this recipe 4.2/5 (5 Votes)


  • For Lamb:
  • 6 1/2 pound leg of lamb, patted dry
  • 4 cloves garlic, 3 smashed into a paste, 1 halved
  • olive oil
  • salt
  • freshly ground black pepper
  • For Gratin:
  • 2 1/2 pounds russet potatoes, peeled and thinly sliced
  • 2 teaspoons chopped fresh thyme, divided
  • 2 teaspoons sea salt, divided
  • 2 teaspoon freshly ground black pepper, divided
  • 6 garlic cloves, minced
  • 4 teaspoons olive oil, divided
  • 2 yellow onions, thinly sliced
  • 1/2 cup dry white wine
  • For Salsa Verde:
  • 2 tablespoons chopped flat-leaf parsley
  • 2 tablespoons chopped fresh mint
  • 1 teaspoon chopped fresh thyme
  • 2 teaspoons Champagne vinegar, plus more as needed
  • 1 teaspoon honey
  • 1/4 cup olive oil, plus more as needed
  • a pinch of salt, plus more as needed
  • a pinch of freshly ground black pepper


Servings 12
Adapted from


Step 1

Prepare Lamb:
Rub garlic paste all over lamb. Rub olive oil all over the leg, then generously season with salt and pepper. Set lamb aside at room temperature for 2 hours.

Prepare Gratin:
Preheat oven to 400 degrees. Choose a baking dish large enough to hold lamb comfortably. Rub interior of dish with the cut side of a halved garlic clove. In the dish, place potatoes, 1 teaspoon thyme, 1 teaspoon salt, 1 teaspoon pepper, garlic, and 2 teaspoons olive oil. Toss everything together and spread potatoes out in an even layer across dish. In a medium bowl, toss 2 yellow onions together with 1 teaspoon thyme , 1 teaspoon salt, 1 teaspoon pepper and 2 teaspoons olive oil. Evenly scatter onions over top of potatoes. Pour wine over vegetables.

Place baking dish with gratin on lowest oven rack. If dish is not large enough to hold lamb and catch all drippings, place a baking sheet or piece of aluminum foil under dish. Place leg of lamb directly on rack above gratin and make sure baking dish is positioned so it catches all drippings. Roast 15 minutes, then lower oven temperature to 350 degrees. Continue roasting lamb until meat thermometer inserted into thickest part registers 125 degrees for medium-rare, about 1¼ hours. (For medium doneness, cook until temperature reads 135 degrees; for medium-well, 145 degrees.) Check gratin after 1 hour of cooking. If potatoes are fork-tender, remove gratin from oven. If the roast needs more cooking time, place (or leave) a baking sheet or aluminum foil on rack beneath lamb to catch drippings. Once lamb reaches desired doneness, transfer to a cutting board and let rest at least 10 minutes.

While lamb and potatoes roast, make Salsa Verde:
In a small bowl, mix parsley, mint, thyme, vinegar, honey, olive oil, salt and pepper. Add more olive oil, vinegar and salt as needed.

Serve lamb with gratin and salsa verde alongside.

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