Heat oven to 375°F and lightly grease a 9-by-13-inch baking dish.
Mix beef, crackers, milk, egg, half the Worcestershire, onion powder, salt and pepper gently and shape eight oval patties.
Brown patties in oil for 2 minutes per side and transfer them to the dish.
Cook sliced onion in the same skillet until soft and scatter it over the patties.
Melt butter in the skillet, whisk in flour for 1 minute, then gradually whisk in broth and remaining Worcestershire.
Simmer gravy for 3 minutes, pour it over the patties and cover the dish with foil.
Bake for 25 minutes until the patties reach 160°F.