Season the steaks as desired. Cook the steaks in a 12-inch nonstick skillet over medium-high heat to desired doneness. Remove the steaks from the skillet. Do not pour off any fat.
Heat the butter in the skillet. Add the mushrooms and cook until they're tender. Stir in the flour and cook for 1 minute. Gradually stir in the stock. Cook and stir until the mixture boils and thickens. Serve the mushroom gravy with the steaks.