Prepare the Mashed Potatoes
Fill a large pot with water and add a pinch of salt. Peel and cut the potatoes into even chunks, then add them to the boiling water. Cook for 15–20 minutes until fork-tender. Meanwhile, warm the milk and butter together in a small saucepan. Drain the potatoes thoroughly, return them to the pot, and mash with a potato masher or electric mixer. Gradually add the warm milk and butter, mixing until smooth and creamy. Season with salt, pepper, and garlic powder if desired, then set aside and keep warm.

Cook the Turkey Filling
Heat olive oil in a large skillet over medium heat. Add the chopped onions and sauté for 3–4 minutes until translucent. Stir in minced garlic and cook for another minute. Add the ground turkey, breaking it apart, and cook until no longer pink, about 6–8 minutes. Season with salt, pepper, thyme, and rosemary as the meat cooks.

Add the Vegetables and Broth
Add diced carrots to the turkey and cook for 3–4 minutes until slightly softened. Stir in the frozen peas and corn, then mix in the tomato paste. Pour in the chicken or vegetable broth and simmer for 5–7 minutes until the mixture thickens slightly. Taste and adjust seasoning as needed.

Assemble the Shepherd’s Pie
Preheat oven to 400°F (200°C). Lightly grease a 9×13-inch baking dish. Spoon the turkey and vegetable filling into the dish, spreading it evenly. Carefully spread the mashed potatoes over the filling, smoothing the top with a spatula or spoon. For texture, create shallow ridges with a fork.

Bake to Perfection
Bake in the preheated oven for 20–25 minutes until the mashed potatoes start to turn golden brown. For a crispier top, broil for an additional 2–3 minutes, watching closely. Remove from oven and let rest 5–10 minutes. Garnish with chopped parsley before serving.

Serving Suggestions
Serve with a simple side salad, roasted vegetables, or warm dinner rolls. Leftovers can be stored in the refrigerator for 3–4 days or frozen for up to 2 months.