Preheat oven to 400 degrees F.
Remove frozen vegetables from the freezer and allow to thaw at least 10 minutes.
While vegetables are thawing, shred cooked or leftover turkey and set aside.
Add broth, buttermilk, butter, thyme, garlic and pepper to an oven safe skillet (we used cast iron) and bring to a boil.
Mix water with cornstarch and add to the skillet. Cook an additional 4 minutes on medium high and remove from heat.
Add peas, carrots, corn, and turkey to the skillet. Stir to combine.
Unroll the puff pastry sheet onto a cutting board lightly dusted with flour. Using a rolling pin, roll out dough 12”
Place puff pastry atop oven safe skillet. Fold extra dough at the edges and crimp using a fork. Cut 4-5 slits in the center
Brush pastry with milk and sprinkle with garlic salt.
Cover with foil. Place into the oven on the center rack and bake for 35 minutes. Remove foil. Bake for an additional 20 minutes, or until the crust is lightly golden. Let stand for 10 minutes before serving