Prepare the meatballs: In a large mixing bowl, combine ground beef, eggs, breadcrumbs, Parmesan cheese, onion powder, garlic powder, and 1 teaspoon of salt. Mix just until combined — don’t overwork the meat or the texture will be dense.
Shape and broil: Using a cookie scoop or your hands, roll the mixture into evenly sized meatballs and place them on a parchment-lined baking sheet. Broil on high for about 8 minutes, turning halfway through, until lightly browned on all sides.
Sauté onion: In a large Dutch oven or deep skillet, melt butter over medium heat. Add thinly sliced onions and sauté until they begin to soften and turn golden.
Build the gravy base: Sprinkle flour over the onions and stir until they are evenly coated. Slowly pour in the bone broth, stirring constantly to prevent lumps. Then, add the Worcestershire sauce and 1 teaspoon of salt to taste. Bring to a gentle boil, then reduce the heat to low.
Combine and simmer: Add the broiled meatballs to the gravy, cover, and let simmer for about 10–15 minutes, until the meatballs are cooked through and the gravy thickens.
Serve: Serve the meatballs and gravy warm over creamy mashed potatoes (or egg noodles) and enjoy that cozy, home-style comfort!