Melt 2 T butter in skillet over medium heat and add the onions, carrots, garlic, celery seeds, parsley, oregano, rosemary, sage, salt, and pepper. Cook until the veggies are soft.
Add chicken broth, and potatoes and bring to a boil. Cook until potatoes are tender but still a bit firm.
In another saucepan, melt 2 T butter over medium heat and add the turkey and flour. Mix and cook until the roux starts to slightly change color. Add milk and mix well, then stir this mixture into the veggie mixture and continue to cook until it thickened.
Set aside to cool a bit.
Preheat oven to 350. Bake bottom crust for about 4-5 mins so that it dries out a bit and stuffing won't make it soggy.
Turn heat up to 425.
Add the cooled mixture to the bottom crust then roll the top crust on, press the edges together, and cut some slits. Brush with egg wash.
Bake for 15 mins then reduce temp back to 350 and continue to bake for another 20 mins or until crust is golden brown.