Tip the whole tin of beans, liquid and all, into a food processor fitted with a metal blade. Add the oil, lemon juice, miso paste, nutritional yeast, garlic and onion powders, chicken seasoning and salt and blend until smooth.
Add the vital wheat gluten and blend until it forms a dough.
Working with about β
rd of the dough at a time, blend the dough for a couple of minutes until it becomes very smooth and stretchy, with a stringy, fibrous looking texture. It should feel tacky but should not stick to your hands. Repeat with the rest of the dough.
Take β
rd of the kneaded dough and stretch it into a long rope with your hands. Twist the rope tightly.
Tie each end into a knot so that it sort of forms one piece. Press it firmly with your hand on the counter top so that it all sticks together. Repeat with the other two pieces of dough.
Fill a slow cooker with hot stock and add the pieces of seitan in a single layer. There should be enough stock to cover them so you may need to add a bit more depending on the size of your slow cooker.
Cook for two hours, flipping halfway through. I have mine set to high but this may vary depending on your slow cooker. You want it to stay at a low simmer, not bubble too much and never boil.
The seitan will expand as it cooks, it is ready when it feels quite firm.
Allow the seitan to cool enough that you can handle it, then either use your hands or two forks to pull it apart into shreds. It is easier to do this while it is still warm. Store in an airtight container in the fridge for up to a week.