In a large bowl, combine the ground beef, breadcrumbs, and egg. Season with salt and freshly ground black pepper. Mix gently to avoid tough patties.

Divide the mixture into 4 equal portions and shape into oval patties about 3/4 inch thick. Press a slight dimple in the center of each to help them cook evenly.

Heat 1–2 tablespoons of oil in a large skillet over medium-high heat. When the pan is hot, add the patties. Brown in batches if needed.

Sear patties 3–4 minutes per side until they develop a deep brown crust. Remove patties and set aside.

Lower heat to medium; pour the can of French onion soup into the skillet and deglaze the pan, scraping any browned bits.

Return the patties to the skillet, spooning some soup over them. Cover and simmer for 12–15 minutes until the internal temperature reaches 160°F.

If a thicker gravy is desired, remove the patties and stir 1 teaspoon cornstarch mixed with 1 tablespoon cold water into the soup. Cook 1–2 minutes until thickened, then return the patties.

Serve the patties hot, spooning plenty of gravy over them. Garnish with chopped parsley if desired.