Heat a little oil in a large pot over medium heat, just enough to cover the surface of the pot.
Add the onion, celery, and carrots and sear them for 5 minutes, stirring occasionally.
Add the chicken broth, garlic powder, ginger, pepper, salt, soy sauce, and sake. Bring to a boil.
Reduce the heat to low and simmer for 30 minutes.
Remove the vegetables from the soup before serving. (You can pick the mushrooms and add them again if you are using shiitake mushrooms for extra flavoring.)
Add the chicken, shrimp, beef, and cook for 5 minutes (optional)
Serve hot. Enjoy!