1) To prepare the seitan, preheat an oven to 375 degrees Fahrenheit. Lightly oil a large cookie sheet and set aside.
2) Combine the wheat gluten and nutritional yeast. Whisk together the water, liquid smoke, tomato paste and tahini and pour into the dry mixture. With your hands, mix together until a ball forms. It will be wet. Knead for a minute or so. Tear nugget-sized pieces of the dough off, flatten and place onto the cookie sheet. Bake 15 minutes, flipping halfway through. Remove from the oven.
3) To make the marinade, combine all of the ingredients for the marinade in a zip lock bag, including the lemon that has been zested and juiced. Toss the baked seitan in the bag and squish it around. Allow the seitan to marinate for at least eight hours, preferably overnight or even for a couple of days. It will only become more flavorful as it sits.
4) Preheat the grill to medium heat. Skewer the seitan pieces and drizzle with some more olive oil to prevent sticking. Grill skewers on each side for a couple of minutes, keeping a close eye on them to make sure they do not burn. Eat as is or make into sandwiches.
To prepare the Chipotle mayo and Sandwich:
1) Combine the vegan mayonnaise and one chipotle pepper in a food processor and blend. Add more adobo sauce from the can for more heat. Assemble the sandwiches on ciabatta bread with the chipotle mayo, thinly sliced onion, fresh oregano, arugula leaves and seitan.
Source of recipe: I wrote this recipe.