Steaming is a simple cooking method that results in clean, pure flavors. In this recipe, we layer sliced fresh shiitake mushrooms in a steamer basket under briefly marinated chicken thighs. The mushrooms soak up the cooking juices, becoming deeply flavorful. Drizzling the chicken with a few tablespoons of sauce after steaming but before slicing allows the sake-soy mixture to better permeate the meat. Serve with steamed rice.