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Fill the espresso machine's metal or ceramic pitcher with enough sake to serve. Note that you should prepare about 3 oz (90 ml) per intended serving. Fill the upper reservoir with water and set the temperature of the espresso machine to low. Allow the water to heat up for about 30 to 60 minutes, or until the temperature reaches 105 degrees Fahrenheit (40.5 degrees Celsius). Open the lid of the upper reservoir and submerge the pitcher of sake in the water. Turn off the heat and allow the sake to sit in the warm water for 30 minutes. Position the pitcher carefully so that none of the water gets inside the mouth and into the sake. Remove the pitcher of sake. Place the steam wand of the espresso machine into the pitcher and turn on the steam to the wand. Let the sake continue heating up until it reaches a temperature of 105 degrees Fahrenheit (40.5 degrees Celsius).  The steam wand should sit at a 45 degree angle to the surface of the sake. Do not allow it to dip into the sake; it must rest above the liquid in order to provide steam. The tip of the wand should also be just a bit off-center. If you want to check the temperature of sake without the use of a thermometer, you can gauge it by looking. If small bubbles begin to rise, the sake is considered to be warm. If bubbles quickly and immediately rise to the surface, then the sake is hot. Remove the steam wand from the sake and serve immediately.  You should be able to handle the pitcher without the use of an oven mitt. If you want to serve the sake in a more traditional way, pour it out of the pitcher and into a tokkuri before serving it to guests.
Pour the sake into the pitcher. Set the temperature to low and let the machine heat up. Submerge the sake in the water. Steam the sake. Remove and serve.