Preheat your oven to 400°F (200°C). Prepare your workspace with a mixing bowl and ingredients.

In the bowl, combine the ground beef, breadcrumbs, milk, onion, garlic, egg, Worcestershire sauce, salt, pepper, parsley, onion powder, and garlic powder until just combined.

Shape the mixture into 1.5-inch meatballs and place them on a baking sheet. Bake for approximately 20 minutes until cooked through.

In a pot, bring salted water to a boil and cook the peeled and chopped potatoes for 15-20 minutes until fork-tender.

Drain the potatoes, return to the pot, add garlic, butter, and milk, and mash until creamy. Stir in parsley, salt, and pepper.

In a frying pan, cook flour for 1 minute, whisk in beef broth and thicken for about 5 minutes. Add soy sauce and mustard; season to taste.

Coat the baked meatballs in the gravy and serve over the garlic herb mashed potatoes.