In a large mixing bowl, combine the ground beef, breadcrumbs, beaten egg, finely diced onion, salt, and black pepper. Mix gently until just combined to maintain the juicy texture. Form the mixture into 6-8 oval patties, about ¾ inch thick.

Heat a large oven-safe skillet over medium-high heat and add a drizzle of oil if desired. Place the hamburger steaks in the hot skillet and cook for about 3-4 minutes on each side until they are golden brown.

In the same skillet, add butter and let it melt over medium heat. Add the sliced onions and sauté for about 5 minutes until softened. Then, sprinkle in the all-purpose flour, stirring constantly for about 2 minutes to form a roux.

Gradually whisk in the beef broth and heavy cream until the mixture is smooth and begins to thicken.

Nestle the browned hamburger steaks back into the rich gravy in the skillet. Cover the skillet with aluminum foil and transfer it to a preheated oven at 350°F. Bake for 45 minutes.

Remove the foil and bake for an additional 15 minutes until the gravy thickens to desired consistency.

Once finished, take the Amish Hamburger Steak Bake out of the oven and let it rest for about 10 minutes.