This is a variation of Warm Japanese Salad with Katsuobushi and Soy Sauce. Salad can be more than a side dish when you combine heated ingredients and cold ingredients. When you eat this, you will not believe that soy sauce is the only seasoning.
Any kind of mushrooms can be used for this salad, but shiitake mushrooms are particularly flavorful and give rich fatty smooth meaty texture when when they are sauteed. Quinoa is not a Japanese ingredient, but adds another interesting texture as well as carbohydrate and other great nutrients.
Feel free to improvise. Use Swiss cards, mustard greens, dandelion greens or other greens instead of kale to bring out little different texture and flavor.