Start by peeling and chopping your potatoes into even chunks. In a large pot, fill with salted water and bring to a boil over high heat. Add the potatoes and cook until fork-tender, about 15 minutes. Drain the potatoes thoroughly and let them sit to steam dry.

In a mixing bowl, combine the hot, drained potatoes with butter, milk, garlic powder, salt, and pepper. Mash until smooth and creamy. Let cool slightly while preparing the filling.

Heat a skillet over medium heat and add olive oil. Sauté diced onion and minced garlic for 2-3 minutes until fragrant and translucent.

Add ground beef to the skillet and cook until browned, about 5-7 minutes. Mix in tomato paste, Worcestershire sauce, mixed vegetables, and broth. Season with salt and pepper and let simmer until thickened.

Preheat oven to 375°F (190°C). Transfer the beef filling into a baking dish and spread evenly. Pipe the creamy mashed potatoes on top, creating ghostly shapes. Add peppercorns for spooky 'eyes'.

Place the pie in the oven and bake for 20-25 minutes until potatoes are golden brown and filling bubbles around edges.