Boil and peel the starchy Russet potatoes. Chop into pieces and place in a pot with cold salted water. Boil until fork-tender, about 15 minutes.

In a mixing bowl, combine hot potatoes with butter, milk, garlic powder, salt, and pepper. Mash until smooth.

Heat olive oil in a skillet. Sauté onion and garlic until translucent, add ground beef and cook until browned. Mix in tomato paste, Worcestershire sauce, vegetables, broth, salt, and pepper. Simmer for 5-7 minutes.

Preheat oven to 375°F (190°C). Spread beef filling in a baking dish, smoothing it out.

Pipe dollops of the mashed potatoes on top, creating ghost shapes. Use peppercorns as the eyes.

Bake for 20-25 minutes until the top is golden brown and bubbly.