1. Wash the spinach thoroughly and put it with the roots first into boiling water. Boil the spinach for about 1 minute. Do not to overcook it.
2. Cool the spinach down under cold water. Then, press the water out of the spinach and cut the spinach into about 2 inches long pieces.
3. Meanwhile, prepare the dressing: Put the miso, sake, brown sugar and sesame into a bowl and mix it well.
4. Add the spinach into the dressing and serve it in small bowls.