Add all ingredients except the seitan powder to a food processor/blender and blend until very smooth.
Transfer to a mixing bowl and add the seitan. Using a wooden spoon, combine everything until it comes together and forms a dough.
Cover the dough and let it rest for 15 minutes.
Divide the dough into two equal pieces and add each piece to a food processor on low/medium speed for 5 minutes. The dough should be very smooth and elastic.
Tightly wrap each piece of dough into a piece of aluminum foil (or a cheese cloth).
Place the parcels in a steaming basket and steam for 2 hours (medium-low temperature). Check back in between to make sure there is enough water in the pot.
Remove the dough parcels from the heat and let them cool down completely. Then you can pull apart the individual seitan strands.