Finely shred some kombu left over from making dashi stock. Add some grated garlic, and a portion of olive oil that is equal that of the other ingredients. Combine and set aside.
Select the small caps of shimeji mushrooms and shred with your hands.
Add 1 teaspoon of the kombu-garlic mixture, and 1 teaspoon of the olive oil from Step 1 and add to a frying pan. Turn the heat to medium.
Mince the onion and add it to the pan to sweat.
When the onion becomes transparent, add the sake and cook briefly.
Remove the ingredients from the frying pan and put them in a bowl. Add the black vinegar, and mix well.
Add the rice to the bowl. Roughly mince the cherry tomatoes and add them as well.
Stir in the miso, and season with salt and pepper. Lastly, add the soy sauce, and adjust the flavor to your liking.
Add the toasted sesame seeds and chopped watercress. Gently mix everything together.
Serve the rice salad up in small dishes, and you are finished.
The recipe makes enough for 3 servings as a side dish. You want to use a small dish, like you might use to serve gelatin or pudding.
If you would rather serve this as part of the main dish, it will make about 1.5 servings.
Story Behind this Recipe
I had planned to use some leftover cooked rice to make rice croquettes, but somewhere during the process I realized my rice was too wet to work with, so I changed plans and added watercress to make a rice salad. I thought it would go well with my main dish, chicken piccata. The flavors combined really well with the seasonings.
The flavour of the dish will change considerably depending on the variety and ripeness of your tomato. I think an acidic and savoury tomato is better than sweet ones. The dish is best once it has cooled, and the flavours have melded. The kombu garlic dressing can be used in many dishes, so make some to keep on hand.