Preheat the oven to 375°F. In a large skillet over medium-low heat melt the butter. Add the onion, celery, and carrot. Cook for 5-8 minutes until softened, stirring occasionally. Add the garlic, thyme, salt, and pepper, stirring constantly until fragrant, 30 seconds. Add the flour and mix with the butter in the pan, let cook for 1 minute. Slowly whisk in the chicken stock and the heavy cream. Let come to a simmer until thickened, whisking occasionally for about 3 minutes.
Take off the heat, stir in the turkey, peas, and corn, set aside.
Grease a muffin tin with baking spray in 8 of the sections, set aside. Roll out the crescent roll dough and cut it into 8 equal squares. Gently press down one square into one of the greased sections on the muffin tin. Make sure the corners are overlapping the sides. Repeat with the rest of the dough.
Evenly fill the cups with the pot pie filling. Fold the corners of the dough over the filling. Bake for 15 minutes or until golden brown. Let the pies cool slightly in the tin before removing them. I find using a butter knife to lift them out the easiest way. Garnish with optional parsley and serve.