Bring large pot of lightly salted water to a boil, add egg noodles and cook for 8-10 minutes or until al dente; drain and rinse under hot water.
In a large skillet, brown the round steak pieces with the onion.
In a slow cooker, combine cream of mushroom,condensed milk, 2 2/3 cups water, sour cream, and steak sauce. Mix until smooth. Add cooked steak pieces, onions, and cooked noodles. Cook on low for 2 hours, to desired taste and constancy.