Seitan is a good protein food, similar to tofu and tempeh in its use as a meat alternative. Its main (and sometimes only) ingredient is wheat gluten, sold as 'vital wheat gluten'. It has a chewy texture similar to chicken. And it has little to no flavour of its own, so you need to add that, either as an ingredient or by marinading, or by both.
I added some gram (chickpea) flour. You don't have to; you can always try alternatives. But this is the recipe for what I did.
3 parts vital wheat gluten
1 part gram flour
heaped teaspoon of onion powder
small dash olive oil
marinade (in this case, a bottle of jerk seasoning because that's what they had in Sainsburys)
Mix the dry ingredients together, then add the dash of oil and stir in water to make a slightly sticky dough. Knead it; it very quickly becomes quite resilient and bouncy, in a way that you'll recognise if you're a bread maker.
Wrap the dough in foil, and steam it. I used a pressure cooker and steamed it under pressure for about 15 minutes. If you don't have a pressure cooker, maybe steam for an hour.
Take the steamed seitan out of the foil, and slice it
Marinade it. As I'm frugal, I pour the marinade on each slice then stack the next slice on top, and then wrap them all back into the foil to seal in the flavour (and keep the flies off, because I'm on a boat and there's lots of flies and no fridge)
Marinade for as long as you like; maybe overnight if you thought that far ahead. In this case, I left it for an hour.
Fry in oil over a fairly high heat. The seitan readily takes on a brown and crispy coat.
Serve. This was the first slice from the pan, and the first time I'd cooked seitan. It was good; a very nice chewy texture. The seasoning was OK, but I'm going to try to create a fuller flavour using tamari, tomato paste, maybe liquid smoke.
The hardest part for me was sourcing the vital wheat gluten. I tried nearly every wholefood shop in Bradford on Avon, Bath and Bristol and none of them had it. Then I found it in the local Co-Op.