Preheat your oven to 400°F (200°C). In a large mixing bowl, combine the ground beef, breadcrumbs, milk, onion, garlic, egg, Worcestershire sauce, salt, pepper, dried parsley, onion powder, and garlic powder. Mix until well combined.

Shape the meat mixture into 1.5-inch meatballs and place them on a baking sheet lined with parchment paper. Bake for about 20 minutes, until golden brown and cooked through.

Boil salted water in a pot. Cook the chopped potatoes for 15-20 minutes until fork-tender, then drain and return to the pot to let steam escape.

Add garlic, butter, and milk to the drained potatoes. Mash until smooth and stir in parsley, adjusting seasoning with salt and pepper.

In a frying pan over medium heat, cook flour until lightly golden. Gradually whisk in beef broth, stirring until thickened. Add soy sauce and mustard, adjust flavors with salt and pepper.

Add the cooked meatballs to the gravy, ensuring they are well-coated. Let them simmer for a few minutes to absorb flavors.

Serve the creamy garlic herb mashed potatoes topped with steak meatballs and gravy. Garnish with fresh parsley.