- In a bowl, mix together ground beef, breadcrumbs, egg, Worcestershire, Dijon, onion powder, garlic powder, salt, and pepper. Form into 16 small meatballs. 
- Heat olive oil in a large skillet over medium heat. Add meatballs and sear until browned on all sides (about 6–8 minutes total). Remove and set aside. 
- In the same skillet, add butter and sliced onions. Sauté until softened (about 5 minutes). 
- Stir in flour and cook for 1 minute. 
- Slowly whisk in beef broth, Worcestershire sauce, and Dijon mustard. Bring to a simmer. 
- Return meatballs to the skillet, cover, and simmer in the gravy for 15 minutes, until fully cooked. 
- Meanwhile, boil potatoes in salted water until fork-tender (about 15–20 minutes). 
- Drain and mash with butter, milk, salt, and garlic powder (if using) until smooth. 
- Serve meatballs and gravy over a bed of mashed potatoes. 
- Garnish with chopped parsley if desired.