Heat the oven to 350°F (175°C) with a rack in the center and grease a 9×9-inch (23 cm) baking dish. Stir the breadcrumbs with ¼ cup of the milk in a large bowl and let them sit for 5 minutes, until they form a thick paste.

Add the beef, egg, 1 tbsp of the Worcestershire sauce, garlic powder, onion powder, salt and ½ tsp of the pepper. Mix gently with your hands, just until no streaks remain. Shape into 4 oval patties about ¾ inch (2 cm) thick and press a shallow dimple into the center of each. Wash your hands afterward, since the mixture contains raw egg.

Heat the oil in a large skillet over medium-high heat until it shimmers and a pinch of breadcrumbs sizzles. Brown the patties for 2 to 3 minutes per side, without moving them, until a dark crust forms and they release from the pan. They will not be cooked through. Transfer them to the baking dish in a single layer.

Reduce the heat to medium and pour off all but 1 tbsp of the fat. Add the onion and cook, scraping up the browned bits, until soft and golden at the edges, 3 to 4 minutes. Stir in the garlic and cook for 30 seconds, until fragrant.

Stir in the soup, the remaining ½ cup milk, the remaining 1 tsp Worcestershire sauce, the thyme and the remaining ¼ tsp pepper. Simmer gently for 2 to 3 minutes, until smooth and bubbling at the edges. Take the skillet off the heat and whisk in the sour cream.

Pour the sauce over and around the patties, spooning some over the tops, then cover the dish tightly with foil.

Bake for 30 to 35 minutes, until the sauce bubbles at the edges and a thermometer in the center of a patty reads 160°F (71°C).

Rest the dish uncovered for 5 minutes, then sprinkle with the parsley, if using, and spoon the gravy over each patty.