What do cottage pie and Corned beef pie have in common?
Corned beef pie:  The pie may be made with a mashed potato topping, as in Shepherd's pie, or with a traditional pastry crust. Shepherd's pie: Shepherd's pie (made with minced lamb or mutton) or cottage pie (made with minced beef) is a meat pie with a topping of mashed potato.
mashed potato topping