Melt 2 tablespoons butter in a skillet over medium heat. Whisk in the flour and cook for 2 minutes until tan.
Slowly whisk in the cooking liquid, Worcestershire and pepper. Simmer for 4 to 6 minutes until the gravy coats a spoon.
Add the cooked beef to the gravy in the skillet. Cover and reheat over medium-low heat, turning gently, until the center reaches 165°F throughout.
Serve immediately, or transfer the hot beef and gravy to a preheated slow cooker set to warm for holding at 140°F or above.
Spread the bread lightly with softened butter and toast it under the broiler or in a skillet until golden.
Put one toast slice on each plate, divide the hot beef over it and spoon on enough gravy to cover the meat without flooding the plate.