How to make the perfect shepherd's pie and the common mistakes to avoid

Comfort on a cold day: shepherd's pie is the perfect winter warmer.
Shepherd's pie and its close cousins, cottage and shepherdless pies have their origins in leftovers. Created as a way to repurpose leftovers from the Sunday roast, this comforting dinner was really just another way of layering up meat, gravy and potatoes. The key components to a good shepherd's pie are flavoursome gravy and fluffy mashed potatoes - the rest is up to interpretation.