Preheat the oven to 350°F (180°C). Line a baking sheet with parchment paper.
In a large bowl, combine the beef, salt, pepper, garlic powder, mustard powder, cayenne, minced onion, eggs, bread crumbs, milk, parsley, and Worcestershire sauce. Mix well until evenly combined.
Split the meat mixture in half and place on the baking sheet. Shape each half into a “foot.”
Press up to form an ankle and hollow out the top to make room for “ankle bones.” Add the halved onion, cut side up, to each divot. Cut 5 toes on each foot and add the reserved slivers of onion to make “toenails.”
Brush around the ankles with ketchup to look like “blood.”
Bake for 1 hour, until the meat is cooked through.