Set oven to 425 degrees and prepare turkey.

Cut potatoes, carrots, and onion. Set onion aside. Put potatoes and carrots in a pot, cover with water. Cover with a lid and boil until not quite fork tender. Drain set aside.

Combine milk, cornstarch, bouillon, onion, salt, and pepper in large pot and bring to a boil whisking constantly. Boil until gravy is thick.

Combine cooked carrots, potatoes, turkey, and corn into gravy mixture and stir.

Prepare crust by whisking together all the dry ingredients into a medium sized bowl. Cut butter in with a pastry blender until it resembles cornmeal. Add water one tablespoon at a time stirring minimally with a fork. Form dough into two disks and roll out.

Place one rolled out crust in the pie pan. Fill with gravy and vegetables mixture. Cover with remaining pie crust. Pinch edges to seal and vent the top. Bake in the oven for 45 minutes.