Slice the beef thinly and set aside.
Cut onion, green onion, carrot, and mushrooms into bite-sized pieces.
Marinate the sliced beef with the sauce (soy sauce, sugar, minced garlic, sesame oil, black pepper).
Place the marinated beef, vegetables, and water in an earthenware pot.
Bring to a boil over medium heat; when the beef is cooked, add glass noodles.
Continue boiling until the noodles are cooked, then finish.