Make the Meatballs:
In a bowl, mix ground beef, breadcrumbs, egg, milk, garlic, onion powder, salt, and pepper. Roll into 1½-inch meatballs.
Brown the Meatballs:
Heat olive oil in a skillet over medium-high heat. Brown meatballs on all sides (they don’t need to be cooked through). Remove and set aside.
Caramelize the Onions:
In the same skillet, melt butter with olive oil. Add onions and sugar. Cook on medium heat for 12–15 minutes, stirring often, until deeply golden.
Build the Gravy:
Stir in flour and cook for 1 minute. Slowly whisk in beef broth and Worcestershire. Add thyme and bring to a simmer.
Simmer Meatballs:
Return browned meatballs to the skillet. Cover and simmer for 12–15 minutes, until meatballs are cooked through and gravy has thickened.
Add Cheese & Broil:
Preheat broiler. Sprinkle shredded cheese over the meatballs and place skillet under broiler for 2–3 minutes, until cheese is melted and bubbly.
Serve:
Garnish with parsley if desired. Serve hot with mashed potatoes, noodles, or toasted bread.