Preheat your oven to 400°F (200°C).

In a large mixing bowl, combine the ground beef, bread crumbs, Parmesan cheese, egg, garlic, onion powder, salt, black pepper, Worcestershire sauce, and parsley. Mix until well combined. Form into meatballs, about 1 inch in diameter.

Place the meatballs on a baking sheet and bake in the preheated oven for 20 minutes, or until cooked through.

While the meatballs are baking, prepare the mashed potatoes. In a pot, bring salted water to a boil and add the cubed potatoes. Cook until tender, about 15 minutes. Drain the potatoes well.

In the same pot, add the cooked potatoes, milk, butter, salt, and pepper. Mash with a potato masher or use an electric mixer until creamy and smooth. Set aside.

For the gravy, combine the beef broth, soy sauce, onion powder, salt, and pepper in a large skillet over medium heat.

In a small bowl, mix cornstarch with water to make a slurry. Add the slurry to the skillet, stirring constantly until the gravy thickens.

Once the meatballs are done baking, transfer them into the skillet with the gravy and simmer for a few minutes to let the flavors meld.

Serve the Salisbury meatballs over the mashed potatoes, spooning some gravy over the top.