Combine beef stew meat, onion, beef broth, vinegar, and bay leaves in a slow cooker.
Cook on Low for 7 to 9 hours.
Bring a large pot of lightly salted water to a boil. Cook egg noodles in the boiling water, stirring occasionally until tender yet firm to the bite, 4 to 5 minutes. Drain.
Remove bay leaves from beef mixture; stir in crushed gingersnaps and brown sugar. Cook beef mixture on Low until thickened, about 15 minutes. Serve sauerbraten over egg noodles and garnish with parsley.