The primary ingredient in traditional shepherd's pie is minced lamb. This dish is a classic of British cuisine, traditionally consisting of a savory filling made with minced lamb, vegetables, and gravy, all topped with a layer of creamy mashed potatoes. While it can be made with other meats, such as beef or even lentils for a vegetarian version, the authentic shepherd's pie uses lamb, which reflects its roots. It's often baked until the potato topping is golden brown and crispy, making it a hearty and comforting meal enjoyed by many.