Shepherd's Pie is a traditional dish of the working class of the British Isles and Ireland for at least 2 hundred years. It consists of minced beef or lamb (for can be turkey or chicken for those looking to reduce fat) and mashed potatoes, plus (usually) carrots and pies.
Both the Irish and British have made meat pies for centuries. Called Shepherd's Pie in Ireland, the English have made a very similar Cottage Pie going back to 1791,. When potatoes were brought to Ireland (and Europe), they became an easily grown source of food for the poor. The term cottage, in England, referred to a small house owned by poor, rural workers; hence the term "cottage pie". The pie in England is made with beef. In Ireland, however, the same dish, made with mutton is called Shepherd's pie. This term is first seen in 1854, . Since then, "Shepherd's Pie", may be used whether the principal ingredient is beef or mutton Still, in the United Kingdom, the term shepherd's pie is typically used when the meat is lamb and if made with beef or other meat, it is called "cottage pie" .
Preheat the oven to 375 F (200 C) .
Peel the potatoes and either use your KitchenAid or other food processor 1/4 to 1/2-inch thin slices or do it manually.
Put the sliced potatoes in a pot ,cover with water, put the lid on and bring to a boil. When it reaches a boil , turn down the heat and leave the lid off to continue simmering until the potatoes are soft, about 15 minutes.
Drain the potatoes in a sieve or colander, discard the water and put the drained potatoes back in the pot.
Mash the either manually or with an electric beater or whisk. Add the half and half, butter, salt and pepper and continue to mash until the lumps are gone and they are smooth.
Mix the in the yolks.
Put the vegetable oil in a pot over medium heat and cook the onion and carrots until they change color, about 5 minutes.
Add the garlic, lamb (or other meat), salt, pepper, thyme and cook until they are brown browned, about 4 or 5 minutes.
Add the tomato paste, chicken broth, Worcestershire, rosemary, thyme, cornstarch and mix well.
Bring to a boil, reduce the heat to low, and simmer until the liquid thickens, about 10 minutes.
Remove from heat and add the peas (note some people also add corn) . Spread the meat mixture evenly into an 11 by 7-inch glass baking dish.. Add the mashed potatoes on top. You want to lay them on top and gently smooth them evenly. It helps to start with the edges and work in towards the middle.
Bake until until the potatoes start to brown; about 25 - 30 minutes, then set on a cooling rack for about 15minutes to set and cool to an edible temperature.
. . Remove to a cooling rack for at least 15 minutes before serving.