To Prepare Seitan
Heat up a frying pan on low heat with oil and sauté the diced onion with salt until the onion softens and is translucent (about 5-7 mins).
Add in the garlic and increase the fire to medium heat, frying for another 2 mins. Add in the paprika and stir for 1 min. Remove from stove and leave it cool for 10 mins.
Once cooled, pour the fried onion into a food processor together with the tomato paste, broth, soy sauce, chickpea flour and nutritional yeast. Blitz until all the ingredients are smooth.
Place vital gluten flour in a medium mixing bowl and pour the blended mixture in. Stir with a spatula so the mixture is firm and continue to knead with your hands. When the dough turns firmer and springy (about 2 mins later), transfer onto plastic cling wrap and roll it up. Wrap in a layer of foil.
Prepare steamer with enough water to steam the seitan log for 1 hour, turning over to the other side mid-way.
Once cooked, remove from steamer and let it cool down to room temperature before unwrapping.
Slice the required amount as needed and keep the balance in airtight container in the fridge.
To Make Vegan Mongolian Beef
Mix soy sauce, coconut sugar, black soy sauce (if using) and water together, set aside.
Mix water and cornflour for slurry, set aside.
Cut the seitan into strips and coat in cornflour.
Heat up a frying pan with oil and pan-fry the seitan strips until slightly brown. Set aside.
In the same frying pan, heat up some oil and sauté the garlic, ginger and dried chillies until fragrant. Toss in the fried seitan and stir for 1 min. Then, pour in the prepared sauce and continue to fry for 1 min. Toss in the spring onion and fry for a few seconds. Pour in the cornflour slurry and fry for 30 seconds, then switch off the fire.
Serve Vegan Mongolian beef with rice and some blanched broccoli.