Boil potatoes in a medium/large stock pot over high heat in salted water. Cook until you can easily poke a fork through them.
Using a stand mixer, hand mixer or potato ricer mash the potatoes with chicken broth, a little butter butter and sour cream. Add the sea salt to taste and set aside
Preheat oven to 395°
Rinse out the stock pot that boiled the potatoes and over medium/high heat add a teaspoon of olive oil and all the ground turkey constantly stirring/ breaking up the meat with a spatula/wooden spoon.
Once turkey is fully cooked remove it from pot and set aside on plate. Leaving the juice/rendered fat behind in the stock pot and add diced onion. Stir and cook onion until fragrant (about a minute) and add in celery, mushroom, carrots and garlic. Sauté until vegetables are cooked and a little tender about 6-8 minutes.
Add peas, corn, flour, tomato paste, worcestershire sauce, chicken stock, rosemary, thyme and cooked meat. Turn heat to low and mix all the ingredients, letting it simmer for 8-10 minutes.
Taste and season with salt and pepper to your liking. Using a casserole or pie dish spread filling evenly across the dish and carefully top with an even layer of mashed potatoes. I usually use a spoon to even this layer out and then a fork to draw a fun design on the potatoes (shown in picture).
Bake at 395° for 20-25 minutes, then switch on the broiler for 1-2 minutes to give the potatoes a nice golden brown color.
Remove from oven and let it cool for 5 to 10 minutes before serving. - Enjoy!