Dice a small onion and saute it in 2 tablespoons of oil for about 3-4 minutes.
Cut 2 portabella mushrooms into small pieces, add to the onions and sprinkle with 1/2 teaspoon of salt and 1 teaspoon of oregano. Then saute the mushrooms and onions for about 5 more minutes until tender.
Add 1 cup of water, 2 tablespoons soy sauce, 2 tablespoons tomato paste, 2 teaspoons paprika, and 2 teaspoons steak seasoning and stir well.
Transfer the mixture to a blender or food processor and blend until it becomes a smooth paste.
Transfer the mixture to a glass bowl and add 1 cup of vital wheat gluten and mix well. Add another 1/2 cup of wheat gluten and mix again.
Add the final 1/4 cup of wheat gluten and knead it in with your hands until you have a firm dough that no longer feels wet to the touch. (You may need to adjust it a little - the amount of wheat gluten needed may vary slightly depending on the amount of moisture in your onion and mushrooms.)
Flatten the gluten dough in a circle on the countertop and cut it into 4 large steaks (or 6 smaller ones.)
Shape the gluten into steaks and fry them in a little oil in a large frying pan. (This sears the gluten and stops it from expanding too much when you simmer them.)
Make the simmering broth
Make a broth by mixing 2 1/2 cups of water 1 tablespoon soy sauce, 1 tablespoon tomato paste, 2 teaspoons steak seasoning, 1 teaspoon smoked paprika, and 1/2 teaspoon garlic powder.
Simmer the seitan steaks
Pour the broth over the seared gluten steaks. This should just barely cover them. Cover with a lid and simmer at a slow boil for 45 minutes. (Flip the steaks after 25 minutes) (Check on the steaks frequently towards the end of simmering to make sure all of the liquid did not evaporate. If the liquid is low add a few more tablespoons. If you still have lots of liquid at the end of cooking simmer for a few more minutes with the lid off. See the picture above of how it should look after simmering.)
After they have simmered for 45 minutes, most of the broth will have been absorbed or evaporated and there will be a little sauce left in the pan. (At this point your seitan is cooked and can be eaten, but if you want to give it a charred steak flavor, grill or sear it in an iron skillet.
Sear your vegan steaks
Heat an iron griddle or skillet until it is very hot. Coat with a small amount of oil and cook the vegan steaks for about 3-4 minutes on each side until it becomes a little blackened. (You can use any of the remaining sauce in the pan as a steak sauce.)
Notes
Wheat gluten is a very fine powder that can get messy. When pouring the flour into the bowl, hold it low in the bowl so it doesn't splash out or make a cloud of dust.
Gluten needs to be cooked, don't eat it raw. You know that it has cooked enough when it is firm and meat-like and no longer has a doughy texture.
After you simmer the seitan for 45 minutes, it is safe to eat, you can then dice it up and use it as vegan beef in other recipes if you wish.
Use only a glass bowl and silicone spatula. Wet gluten is very sticky and hard to clean.
Wash your bowl and utensils in very hot water. This will help to reduce the stickiness of the gluten. You may want to use an old rag that you can throw away after you clean up.