In a large pot, bring salted water to a boil. Add peeled and chopped potatoes and cook until fork-tender, about 15-20 minutes. Drain well.
Add the butter, milk, salt, and pepper to the drained potatoes. Mash until smooth and creamy. Stir in shredded cheese if using. Set aside.
In a large skillet, sauté the diced onion and minced garlic over medium heat until softened, about 5 minutes. Add the shredded turkey, turkey broth, mixed vegetables, thyme, sage, salt, and pepper. Stir and let simmer for about 5 minutes to ensure everything is heated through.
Gently fold in the leftover stuffing into the turkey mixture. Ensure it’s evenly distributed and remove from heat.
Preheat your oven to 375°F (190°C). In a greased 9x13 inch baking dish, spread the turkey and stuffing mixture evenly. Top with the mashed potatoes, spreading them out carefully to cover the filling completely.
Place the dish in the preheated oven and bake for 25-30 minutes, or until the top is golden brown and the filling is bubbling.
Let the pie cool for a few minutes before serving. Garnish with fresh herbs if desired for a festive touch.
Notes
Optional to garnish with fresh herbs before serving.