In a large pot filled with water, add the cut potatoes and some salt. Bring to a boil until the potatoes are soft then drain. Mash the potatoes until smooth with a stick of butter and some milk. Season to taste with salt and pepper then set aside.
In a large pan on medium high heat, add 1 Tbsp of olive oil and the ground meat. Brown the meat then season with salt and pepper. Remove from the pan and set aside.
In the same pan, discard the fat (if any) and reduce the heat to medium. Add 3 Tbsp of butter and the diced onions. Caramelize the onions slightly then add the carrots and celery. Cook for around 5-7 minutes then add the garlic, thyme, and tomato paste. Bloom the tomato paste, then mix into the veggies. Sprinkle in some flour, and mix.
Next add the wine and bring to a simmer. Add the beef stock, Worcestershire sauce, and ground meat back to the pan. Let reduce and simmer on low heat until the filling is thickened and the vegetables are soft, about 15-20 minutes. (Add more stock if needed). Add the peas to the pan and season with salt and pepper to taste.
Next in a lightly greased 9x13 casserole dish, spread the meat mixture evenly in the bottom of the pan making sure to pack it in tightly. Spread the mashed potatoes over top of the meat filling evenly and top with a generous layer of Parmesan cheese.
Bake in the oven set to 375 degrees Fahrenheit for 35 minutes then place under the broiler for about 3-5 minutes to brown the parmesan cheese. (Make sure to keep a close eye on it so the cheese does not burn). Let the shepherds pie rest for 20 minutes.
Slice, serve and garnish with parsley.
Enjoy!
