- Make the filling: In a large dutch oven or pot, melt butter over medium heat and cook onions, garlic, salt, pepper, and thyme. Cook until onions are translucent, about 15 minutes. Add flour and stir, then slowly add stock while whisking; mixture will thicken. Add lemon zest, turkey, and vegetables. Take off heat and stir well to combine. Place in a 9-inch cast-iron skillet or baking dish and set aside.
- Make the biscuits: Preheat oven to 400 degrees. In a large bowl, combine flour, baking powder, baking soda, salt, sugar, and cold butter. With your fingers or a fork, cut cold butter into flour until it’s the size of small peas. Make a well in center and add cold buttermilk. With a fork, gently incorporate dry mixture with buttermilk until a dough forms. On a lightly floured surface, pat out dough into a rectangle, about ½-inch thick.
- Cut out biscuits and place on top of pie filling, making sure they are slightly spaced out (they will expand while baking). Brush biscuits with buttermilk and sprinkle with thyme leaves. Bake for 40 to 45 minutes until golden brown and bubbly. Remove from oven and brush with melted butter. Let cool slightly before serving