Make fish stock according to the directions in the Notes section. Flavor stock with soy sauce, sake and salt. Add daikon radish, carrot, shiitake mushrooms and salmon. Boil until soft (roughly five minutes).
Meanwhile, toast rice cakes until they puff up and brown. It takes about six to seven minutes. They should look like oversized marshmallows.
In each deep soup bowl, lay one rice cake on the bottom and arrange other ingredients against it. Add stock and top with salmon roe and a few sprigs of trefoil and or yuzu peel. Serve immediately.
How to make Konbu Dashi Stock:
Take a 6-inch piece of kelp (konbu), wipe lightly with a damp cloth and put into a pot with 6 cups water. Bring to a boil and remove kelp. Add a generous 3/4 cup of dried bonito shavings (katsuobushi) and boil for one minute. Turn off heat and after 2 minutes, strain.