Chicken breast and firm tofu have plenty of protein! This dish has fewer calories so I recommend it for those on a diet. The ingredients are cheap. It's great as a side dish to have in stock in your fridge.
This is a dish I always have on stock in my refrigerator.
Making sure there's no moisture left is a hint for preserving it, perhaps? If you add the shiitake last they'll absorb the moisture.
Enjoy Japanese food around the world.