Cut the beef and vegetables into bite-sized pieces.
Add beef to a pot and stir-fry over medium heat.
When the beef is half cooked, add vegetables such as onion, carrot, and potato, and stir-fry together.
Add soy sauce, minced garlic, pepper, and water, and bring to a boil.
Cover and simmer over low heat until the beef and vegetables become tender.
Add green onions to finish, if desired.