In a large bowl, mix together 1/3 cup condensed French onion soup with ground beef, bread crumbs, egg, 1 tsp. Worcestershire sauce, 1/4 cup ketchup, ½ cup chopped onion, 1 tsp. onion powder, salt and black pepper. Shape into 6 oval patties.
In a large skillet over medium-high heat, brown both sides of patties in 1 tbsp. butter and 1 tbsp. olive oil. Remove patties to a plate; pour off excess fat from skillet.
In a small bowl, blend flour and remaining soup until smooth; mix in remaining ingredients. Pour into skillet and stir until thicken. Reduce heat, add patties and spoon sauce over them. Cover, and cook for 20 minutes, stirring sauce occasionally.