In a large Pyrex mixing bowl, combine 2 pounds uncooked stew beef, 1 can condensed cream of mushroom soup, 1 envelope of onion soup mix, and 1 soup can of water. Stir until blended. Cover the Pyrex mixing bowl with aluminum foil and place it in an oven that has been preheated to 350 degrees. Cook for about 2 hours, checking occasionally for doneness, and stirring the stew beef mixture. When the gravy is thickened (somewhere from 2 to 2 .5 hours), remove the stew meat mixture from the oven and place it in a serving bowl. In the meantime, prepare the 12 oz. of egg noodles according to the package instructions. Drain with a colander and remove the noodles to a serving bowl. Mix 1/2 tablespoon of butter with the noodles. Serve this beef and noodle dish by placing the desired amount of noodles on a serving plate and topping them with the prepared stew beef and onion gravy. Serve while hot!