Preheat oven to 375 degrees. Fit baking sheet with a wire rack and coat with cooking spray. Set aside.
Mix together chopped turkey, stuffing and mashed potatoes in a bowl until thoroughly combined, like meatloaf. Using your hands, roll mixture into about 16 medium-sized balls.
In a small bowl, whisk together egg and milk. Place breadcrumbs in a medium-sized bowl. Coat each ball with egg wash, then breadcrumbs and place on the wire rack.
Coat balls with cooking spray. Bake for 15 minutes, until outside is crispy. Turn oven to a low broil and toast balls for about 4 minutes, turning occasionally so all sides are evenly browned. Serve with reheated gravy or cranberry sauce.