Wash the sweet potatoes thoroughly, peel them, and cut them into bite-sized pieces.
Cut the beef into bite-sized pieces.
Pour water into a pot and add the beef first to bring it to a boil.
Skim off any foam, then add the sweet potatoes.
Add soy sauce, garlic, pepper, and other seasonings, and simmer over medium heat until the sweet potatoes are cooked through.
When the sweet potatoes and beef are fully cooked, season with salt to taste.
Serve the finished sweet potato soup in a bowl.