A long time ago I tried to make seitan - wheat gluten - and failed miserably. This time it worked a lot better. Seitan is the oldest known meat substitute, having been used in China for ages. It has a very spongy texture, and absorbs soup or sauce flavors very well - much better than tofu.
a bunch of flour (two cups, maybe?)
enough water to make a thick dough
Stir together flour and water. Add a bit more flour, and keep stirring and adding flour until it's getting kind of annoying to try and push the spoon around. Knead the dough until it is not sticky, plus twenty minutes. This step is annoying, but kneading is what convinces the gluten to lock into its matrix, and you want it to all decide to do that. Then start kneading the dough inside a bowl full of water; white starch will start coming off the dough, leaving the stringy gluten behind. Periodically, lift the dough up out of the water and squeeze all the water out of it. When you do this, you will probably end up with wierd rubbery dangling strings; just grab them and fold the back onto the dough, and fold the dough over itself a couple of times every so often. The dough should gradually get slippery and rubbery, without any solid areas, just gloopy tangles. You may want to dump out your bowl of water and refill it periodically, as all the starch in the water will make it cloudy and hard to see.
Continue until the water you squeeze out of the gluten is almost clear. At this point, toss the gluten in the refrigerator for a couple of hours with whatever spices you'd like to flavor it with. I used Maggi HOT (a yeast extract sauce with some capsaicin in) and a bit of garlic powder.
Gluten works well in soups, though it tends to be a bit spongy. Put it in early so it has a chance to absorb lots of flavor from the broth. Sauteeing is good, too - since gluten is protein (just no animal protein) it will sear and crisp in a very meatlike way (though the inside will be bubbly). It won't fool anyone in a soup, but sauteed in small enough pieces, it might.
Gluten one buys professionally is denser and less spongy than this, and I plan to experiment on ways to press it or shape the strings or something.