In a large mixing bowl, combine ground beef, finely chopped onion, minced garlic, breadcrumbs, beaten egg, Worcestershire sauce, salt, and pepper. Mix well until all ingredients are evenly incorporated.

Heat a large skillet over medium heat, adding a splash of olive oil. Once hot, place the patties in the skillet, cooking for about 4-5 minutes on each side until browned.

In the same skillet, pour in the beef broth or gravy, and bring to a gentle simmer. Whisk in flour gradually to create a smooth sauce, stirring continuously.

Preheat your oven to 350°F (175°C). In a greased baking dish, arrange the cooked patties in a single layer. Pour the thickened gravy evenly over the patties.

Cover the baking dish with aluminum foil and bake for 20-30 minutes, uncovering during the last 5-10 minutes if you’ve added cheese.

Let the casserole cool slightly, then serve warm alongside mashed potatoes or a fresh green salad.