Dough: In a large bowl stir together all dough ingredients until a ball forms. Transfer to a clean surface and knead for about 5 minutes, or until dough is elastic and cohesive (it will still be lumpy, that's okay!) Form into a rectangle, working it to be about ½ inch thick (you may need to use a rolling pin). Cut into four even rectangles, then let dough rest for 5 minutes while you prepare the broth.
Broth: Add all broth ingredients to a large pot and bring to a simmer. Gently lower the seitan steaks into the broth, ensuring the dough is covered by the broth (if not, transfer to a smaller pot). Partially cover and simmer for 30 minutes.
Marinade: Meanwhile, whisk together all marinade ingredients until sugar is dissolved. Remove steaks from the pot and let cool enough to touch, then brush with the marinade. Let sit in the marinade for 15 minutes (up to 8 hours).
Sear: Sear on a well greased pan or grill over high heat to slightly char the outside, then serve warm.