01 - Preheat the oven to 400°F.
02 - Pat the leg of lamb dry with paper towels and rub evenly with olive oil, sea salt, and black pepper.
03 - Place potatoes, sliced onion, and crushed garlic in a large roasting pan. Drizzle with olive oil, season with salt and pepper, and toss to coat. Scatter rosemary and thyme sprigs over the vegetables.
04 - Position the lamb atop the vegetables. Pour dry white wine and broth into the roasting pan around the lamb without pouring over it.
05 - Roast in the oven for 1 hour and 20 minutes for medium-rare, basting occasionally with pan juices. Cover loosely with foil if potatoes brown too quickly.
06 - Remove the lamb from the oven and tent with foil. Allow it to rest for 15 minutes before carving.
07 - Increase oven temperature to 430°F and return the potatoes to the oven for an additional 10 minutes, if needed, to achieve a crisp finish.
08 - Slice the lamb and serve alongside the roasted potatoes with pan juices.