Place the beef cubes, diced onion, and sliced mushrooms into the slow cooker.
1½ pounds stewing beef or chuck roast, 1 small onion, 1 cup mushrooms
Add the cream of mushroom soup, beef broth, Worcestershire sauce, garlic powder, salt, pepper, and parsley. Stir gently to combine.
1 can, 1 cup beef broth, 1 tablespoon Worcestershire sauce, 1 teaspoon garlic powder, ½ teaspoon salt, ½ teaspoon black pepper, 1 teaspoon dried parsley
Cover and cook on Low for 6–8 hours or High for 4–5 hours, until the beef is tender and easy to shred with a fork.
During the last 15–30 minutes of cooking, stir in the sour cream. Let it warm through until creamy and smooth.
¾ cup sour cream
While the stroganoff finishes, cook the egg noodles according to package instructions. Drain well.
8 ounces egg noodles
Spoon the rich beef stroganoff over a bed of warm egg noodles and serve hot.