Place the peeled, cubed potatoes in a large pot of salted water. Bring to a boil. Cook for 15 to 20 minutes, until tender. Drain thoroughly and set aside.

Return the drained potatoes to the pot. Add the unsalted butter, milk, garlic powder, salt, and black pepper. Mash until smooth and creamy.

While the potatoes cool, cook the ground beef in a skillet over medium heat. Stir in the onion powder and Worcestershire sauce. Cook thoroughly, reaching 160°F on a food thermometer. Drain excess fat.

Preheat the oven to 375°F.

Divide the mashed potatoes among 12 standard muffin wells. Press firmly to form an even base in each well.

Add a spoonful of cooked beef to each potato base. Divide the shredded cheddar cheese and crumbled bacon evenly over the beef.

Bake for 15 to 20 minutes, until the tops become lightly golden and crisp.

Remove the tin and sprinkle grated Parmesan cheese over each cup. Return to the oven for another 5 minutes.

Let the cups rest for about 5 minutes before gently loosening their edges. Lift carefully from the tin, garnish with chopped parsley, and serve.