Grind perilla seeds to make perilla powder.
Rinse the tofu noodles in cold water and drain well.
Pour water into a pot and bring to a boil.
Add the tofu noodles to the boiling water, blanch them for 1-2 minutes, then drain.
Add perilla powder, water, and salt to the pot. Simmer over low heat, stirring continually.
Place the tofu noodles in a bowl and pour the perilla broth over them.
Top with green onion and roasted seaweed flakes, if desired.