In 5- to 6-quart Dutch oven, melt butter over medium-high heat. Add onion, garlic and mushrooms; cook 5 to 6 minutes, stirring frequently, until mushrooms are softened.
Stir in beef. Cook 5 to 6 minutes, stirring frequently, until beef is no longer pink. Stir in remaining ingredients except noodles and sour cream. Heat to boiling. Reduce heat to medium-low; cover and cook 10 minutes, stirring occasionally. Stir in noodles. Cover; cook 5 to 7 minutes, stirring occasionally, until noodles are tender.
Stir in sour cream. Cook 3 to 5 minutes, stirring frequently, until well blended.