Preheat your oven to 400°F (200°C) and prepare a baking sheet lined with parchment paper.

In a large mixing bowl, combine ground beef, breadcrumbs, milk, onion, garlic, egg, Worcestershire sauce, salt, pepper, parsley, onion powder, and garlic powder.

Shape the mixture into 1.5-inch meatballs and place them on the baking sheet.

Bake the meatballs for approximately 20 minutes or until golden brown.

Meanwhile, boil salted water and cook chopped potatoes until fork-tender, about 15-20 minutes.

Drain the potatoes, then mash them with garlic, butter, and milk. Season with salt, pepper, and chopped parsley.

In a frying pan, cook flour for 1 minute, then whisk in beef broth, soy sauce, and mustard. Simmer for 5 minutes until thickened.

Add baked meatballs to the gravy, coating them well.

Serve the meatballs over the mashed potatoes, garnished with parsley.