Preheat oven to 375°F. Brush a 9x13-inch baking dish with 1 tbsp melted butter.
Toss sliced potatoes and onions with olive oil. Spread evenly in the prepared dish and dot with remaining butter.
Whisk soup, broth, 2 tsp Worcestershire, Dijon, and cornstarch in a bowl until smooth. Set the gravy aside.
Combine beef, crushed crackers, beaten egg, milk, 1 tbsp Worcestershire, garlic powder, onion powder, salt, and pepper.
Form six oval patties about 3/4 inch thick. Sear in a hot skillet 2–3 minutes per side until browned.
Nestle browned patties over the potato-onion layer. Pour the gravy evenly over everything.
Cover tightly with foil and bake 30 minutes. Uncover and bake 15 minutes more, until potatoes are tender and beef is cooked through.
Rest 5 minutes, then sprinkle with parsley and serve warm.