Put the soy milk and soup stock granules in a heat-resistant bowl. Microwave for 1 minute and mix well. Make sure the soup stock granules are fully dissolved. Let cool.
Beat the eggs in a separate bowl and strain through a sieve. Mix into the mixture from Step 1.
Place the heat-resistant bowl into a pot and fill the pot with hot water to halfway up the sides of the bowl. Cover and cook over a high heat for a little less than a minute. Reduce the heat to low and cook for 11 minutes.
Scoop the cooked egg tofu from Step 3 and transfer to a serving dish. Dilute the mentsuyu with water and pour over the top. Top with chopped mitsuba or yuzu, if available. Enjoy.
Story Behind this Recipe
This recipe is based on one for regular chawanmushi (steamed savory custard).
If the soup stock granules are not fully dissolved after microwaving the soy milk mixture, reheat in 10-20 minute increments until dissolved. Microwave for less than a minute at a time, watching while microwaving to make sure the soy milk does boil over. In Step 3, make sure that the hot water does not get inside the bowl. Be careful not to overcook the egg tofu.
Mentsuyu can be replaced with the sauce that accompanies natto.