Add the vital wheat gluten, nutritional yeast, smoked paprika, onion powder, garlic powder and red pepper flakes to a mixing bowl and mix together.
Add the vegetable stock, canola oil, tamari, tomato paste, maple syrup, liquid smoke and dijon mustard to a bowl or measuring jug and whisk together and then add to the dry ingredients and mix into a thick dough.
Knead the dough for 2 minutes until it feels firm to the touch. Break it into two pieces and form it into two sausage shaped logs. It won't be perfect at all, but just press it into the shape the best you can.
Wrap the sausage logs in parchment paper and then in foil, don't wrap the foil too tight as the pepperoni can expand slightly when steaming.
Steam in a steamer basket over boiling water for 40 minutes. If some oily residue appears in your steamer basket, don't worry about it, this is normal.
Let the pepperoni cool on the countertop and then place into the fridge until chilled.
Unwrap it from the foil and parchment paper and your vegan pepperoni is ready to be used!