01 -
In a large bowl, combine the ground beef, breadcrumbs, egg, dry mustard, garlic powder, salt, and black pepper. Mix everything together gently with your hands or a fork until just combined. Be careful not to overmix, as this can make the meatballs tough.
02 -
Using your hands or a cookie scoop, portion the meat mixture into 1½-inch meatballs. Roll each portion between your palms to form smooth, round balls. This recipe should make approximately 16 meatballs.
03 -
Heat a large skillet over medium heat. Add the butter and olive oil to the pan. Once the butter has melted and the oil is hot, carefully add the meatballs in a single layer, working in batches if necessary to avoid overcrowding. Sear each meatball for about 3-4 minutes per side, turning occasionally to ensure even browning. Once browned on all sides, transfer the meatballs to a plate. They don't need to be fully cooked at this stage.
04 -
In the same skillet with the remaining fat, add the thinly sliced onions. Reduce the heat to medium-low and cook the onions slowly for 12-15 minutes, stirring occasionally. This slow cooking process allows the onions to caramelize and develop a deep, sweet flavor and golden-brown color.
05 -
Increase the heat back to medium. Pour the beef broth into the skillet with the caramelized onions, and add the Worcestershire sauce. Use a wooden spoon to scrape up any browned bits (fond) from the bottom of the skillet - these add tremendous flavor to the gravy.
06 -
In a small bowl, whisk together the cornstarch and water until smooth to create a slurry. Slowly pour this mixture into the simmering broth while stirring constantly to prevent lumps from forming. Allow the gravy to simmer for 8-10 minutes, stirring occasionally, until it thickens to your desired consistency.
07 -
Taste the gravy and adjust the seasoning with salt and pepper according to your preference. Remember that the meatballs will add more flavor when they're returned to the gravy.
08 -
Return the browned meatballs to the skillet, spooning some of the gravy over each one. Cover the skillet and reduce the heat to low. Let the meatballs simmer in the gravy for about 5 minutes, or until they're cooked through to an internal temperature of 165°F.
09 -
Sprinkle freshly chopped parsley over the meatballs and gravy for a pop of color and fresh flavor. Serve hot, ideally over creamy mashed potatoes to soak up all that delicious gravy.