Shepherd's Pie is a classic British comfort food, but there is a specific rule about its name. To be a true 'Shepherd's Pie,' the meat used must be lamb, as shepherds herd sheep. If the dish is made with beef, it is correctly called a 'Cottage Pie.' The dish originated as a way for peasant families to use up leftover roasted meat and prevent food waste. The 'crust' of the pie is made from mashed potatoes, which were introduced to the UK in the late 16th century and became a cheap staple for the working class. Historically, the potato topping was often scored with a fork to create peaks that would brown and become crispy in the oven, providing a textural contrast to the soft filling beneath.