Preheat your oven to 400°F (200°C).

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

Shape the meat mixture into 1.5-inch meatballs and arrange on a greased baking sheet. Bake for about 20 minutes.

While meatballs bake, boil water in a pot, add chopped potatoes, and cook until fork-tender, about 15-20 minutes.

Drain the potatoes, return them to the pot, and add minced garlic, butter, and milk. Mash until smooth and creamy, then stir in chopped parsley and season with salt and pepper.

For the gravy, heat flour in a frying pan, whisk in beef broth until thickened, then add soy sauce and Dijon mustard.

Add the baked meatballs to the gravy and gently toss to coat. Allow to simmer for a few minutes.

Serve meatballs drenched in gravy alongside garlic herb mashed potatoes, garnished with parsley if desired.