1. For the marinade, mix the pomegranate molasses, oil, garlic, cayenne, and thyme in a zippered plastic bag. Add the lamb and season with salt and pepper. Refrigerate for at least 4 hours, occasionally turning the bag over.

2. To make the vinaigrette, combine the shallot, vinegar, and pomegranate molasses in a bowl and let stand for 15 minutes. Whisk in the walnut and olive oils. Season with salt and pepper.

3. Preheat the oven to 375°F (190°C). Heat an ovenproof frying pan over high heat. Remove the lamb from the marinade. Add to the pan and cook, turning occasionally, about 10 minutes, until browned. Roast for about 10 minutes, until an instant-read thermometer inserted in the center of the lamb reads 130°F (55°C) for medium-rare. Transfer the lamb to a carving board and let stand for 10 minutes.

4. Carve the lamb. Divide the mesclun and endive among dinner plates and top with the sliced lamb. Sprinkle with the walnuts and pomegranate seeds. Drizzle with the vinaigrette and serve immediately.