Melt butter in a large soup pot over medium heat.
Add sliced onions and cook over medium heat until caramelized. Stir regularly to prevent burning. Onions will be a rich golden brown color.
Add in beef broth, cooking sherry, sugar, flour, salt, and worcestershire sauce. Whisk until smooth.
Add bay leaves, thyme sprigs, and egg noodles
Bring soup to a boil; reduce heat and simmer 30 minutes or until noodles are fully cooked.
Top with shredded cheese; garnish with fresh thyme and ground pepper.