Put peeled and cubed potatoes in a pot of boiling water for about 15 minutes or until they are fork tender (or make in Instant Pot for 6 minutes with a bit of broth). Drain, set aside to cool a bit. While the potatoes are cooking, heat the oil for frying and add the onions to the pan. Fry on low heat for 5 minutes, stirring. Then add the garlic and sauté for 1 more minute.
Add ground turkey and fry everything together for another 3 minutes, stirring occasionally until meat is no longer pink. Add all-purpose flour and mix, fry for another 2 minutes. Add beef broth, tomato paste, Worcestershire sauce, salt and pepper. You can also add any other spices to taste.
Stir and cook everything together for 6-7 minutes until the broth becomes thicker. Add the frozen vegetables, stir and turn off the heat after 2 minutes. Transfer the filling to a baking dish. My oval baking dish is 11 inches long and 7 inches wide. Preheat the oven to 360 F.
Add drained tender potatoes into a bowl and add whipping cream or sour cream, salt, butter and parmesan. Make mashed potatoes. Spread the mashed potatoes on top of the minced meat filling.
Put the pie in the oven and bake for 30 minutes or until browned on top. If you wanted to sprinkle on some shredded cheese on top do so for the last 10 minutes to melt and brown.