The main ingredient in traditional shepherd's pie is minced lamb. Shepherd's pie is a savory dish that consists of a base of lamb cooked with vegetables, typically onions, carrots, and peas, all covered with a layer of mashed potatoes. The dish is baked until the potatoes are golden and crispy on top. Traditionally, shepherd's pie is distinguished from cottage pie, which uses minced beef instead of lamb. The dish has its origins in the British Isles and is known for its comforting qualities and versatility, allowing variations in both the filling and the topping.