Add the beef stew meat, sliced mushrooms, diced onion, minced garlic, beef broth, Worcestershire sauce, paprika, salt, and black pepper to the slow cooker. Stir to combine.

Cover and cook on low for 7 to 8 hours until the beef is very tender.

In a small bowl, whisk the cornstarch with 2 tablespoons of cold water. Stir this mixture into the slow cooker and cook on high for 15 minutes to thicken the sauce.

Stir in the sour cream until the sauce is smooth and creamy. Turn the slow cooker to warm.

Cook the egg noodles according to package directions. Drain them and toss with the butter until coated.

Spoon the beef and mushroom mixture over the buttered noodles. Sprinkle with chopped parsley before serving.