Begin by peeling and chopping your potatoes into evenly sized pieces, then place them in a large pot filled with cold salted water. Bring to a boil and cook for about 15 minutes or until fork-tender. Drain and set aside.

Mash the hot potatoes with butter, milk, garlic powder, salt, and pepper until smooth. Let cool slightly before piping. Transfer to a piping bag fitted with a large star tip.

In a skillet, heat olive oil over medium heat. Add onions and garlic, sauté for 2-3 minutes. Then, add ground beef, breaking it apart, and cook until browned, about 5-7 minutes.

Stir in tomato paste, Worcestershire sauce, mixed vegetables, beef broth, salt, and pepper. Cook on medium heat for 5-7 minutes until simmering and thickened.

Spoon the beef filling into a 9x9 baking dish. Use the piping bag to create ghost shapes over the filling. Press peppercorns into the mash as eyes.

Preheat oven to 375°F (190°C) and bake the assembled pie for 20-25 minutes until the topping is golden and filling is bubbly.