01 -
Set your oven to 350°F (175°C) and let it heat up.
02 -
Drop the butter into a skillet warmed over medium heat. Toss in the onions, stirring occasionally, until they turn sweet and golden (around 20-25 minutes). Pour in some beef broth to scrape up the browned bits, then stir until the liquid disappears. Cool them off afterward.
03 -
Toss the ground beef, breadcrumbs, garlic, milk, egg, Worcestershire sauce, Dijon mustard, thyme, salt, and pepper into a big mixing bowl. Stir until everything's mixed up nicely.
04 -
Mix half of the cheese and the cooled onions into the meat mixture. Form it into a loaf shape and set it into your baking dish.
05 -
Pop it in the oven and let it cook for about an hour, or until it hits 160°F (70°C) inside.
06 -
Sprinkle the rest of the shredded cheese over the top and bake for another 5-10 minutes until it’s bubbly and melted.
07 -
Once it's out of the oven, let it sit for 10 minutes before cutting. Serve with whatever sides you like best.