1. In a large bowl combine the ground beef, breadcrumbs, milk, egg, Worcestershire sauce, Dijon mustard, onion powder, garlic powder, smoked paprika, salt, and pepper, and gently mix until evenly combined without overworking the meat.

2. Scoop the mixture into portions about one and a half tablespoons each, roll into meatballs, and place them on a plate or tray.

3. Heat the olive oil in a large skillet over medium high heat, add the meatballs in a single layer, and brown on all sides before transferring them to a plate.

4. Reduce the heat to medium, add the butter, and cook the sliced onions with a pinch of salt until soft and lightly caramelized, then stir in the minced garlic.

5. Sprinkle the flour over the onions, stir to coat, and cook for one minute to remove the raw flour taste.

6. Slowly pour in the beef broth while stirring constantly, scraping up browned bits, until the gravy base is smooth and slightly thickened.

7. Stir in the Worcestershire sauce, Dijon mustard, ketchup if using, dried thyme, salt, and pepper, and simmer for three to five minutes until glossy and thick.

8. Nestle the browned meatballs and any juices back into the skillet, spoon gravy over the top, cover, and simmer on low for ten to twelve minutes until the meatballs are cooked through.

9. Taste the gravy, adjust seasoning, sprinkle with chopped fresh parsley, and serve the meatballs hot over mashed potatoes, noodles, or rice.