In a large mixing bowl, combine the ground beef, breadcrumbs, milk, egg, chopped onion, minced garlic, Worcestershire sauce, salt, black pepper, garlic powder, and onion powder. Mix until well combined.
Shape the mixture into golf ball-sized meatballs, producing about 12-15 meatballs.
Heat olive oil in a skillet over medium heat. Once hot, carefully add the meatballs, making sure not to overcrowd the pan. Brown on all sides, about 6-8 minutes.
Once browned, gently pour the beef broth over the meatballs in the skillet.
Reduce the heat to low, cover, and let the meatballs simmer in the broth for 15-20 minutes, or until cooked through (internal temperature should reach 160°F).
If you prefer a thicker gravy, mix the cornstarch with water in a small bowl until smooth, then stir it into the skillet. Allow it to simmer for an additional 2-3 minutes until thickened.
Serve the Salisbury Steak Meatballs hot, spooning the gravy over them. Enjoy with mashed potatoes or your favorite side.