Preheat oven to 400 degrees Fahrenheit.
Prep the Vegetables and Pastry: Cut carrot, celery, and mushrooms into ½-inch pieces. Cut the puff pastry into 2 ½-inch squares and set aside.
2 stalks celery, 1 ½ cup carrots, 4 ounces mushrooms, 2 sheets puff pastry
Warm olive oil in skillet over medium heat, then add chopped carrot and celery pieces and saute until tender, stirring occasionally (about five minutes). Remove from heat.
2 teaspoons olive oil
Make the Filling: Add turkey, gravy, mushrooms, peas, herbs and spices to pan and stir until the meat and vegetables are evenly coated.
2 pounds turkey, 6 cups gravy, 1 cup peas, 1 teaspoon dried thyme, ½ teaspoon rubbed sage, ¼ teaspoon cayenne pepper
Assemble and Bake: Lay the puff pastry squares over top of the filling in an overlapping pattern then brush them with the beaten egg. Transfer the pan to the oven and bake for about 35 minutes or until the crust is golden brown and the filling is warmed through and bubbly.
1 egg