Preheat the oven to 170 °C.
To make the seitan, place all the seitan ingredients except for the vital wheat gluten and vegetable suet in a high-speed blender and blend until completely smooth. If your mixture isn’t quite smooth, pass it through a fine mesh sieve to remove any chunks.
300 g silken tofu, 200 g cooked beetroot, 55 g vegetable oil, 30 g English mustard, 1 tablespoon vegan beef stock powder, 2 tablespoon nutritional yeast, 1 ¼ tablespoon fine sea salt, 1 tablespoon rice vinegar, 2 tablespoon dark soy sauce
Return the blended mixture to the blender and add the vital wheat gluten. Blend until you have a rough dough then stop the blender and leave to rest for 10 minutes. Blend again for at least 2 minutes or until the seitan is lumpy, stretchy and very gummy.
440 g vital wheat gluten
Add the vegetable suet to the blender and pulse a few times until the suet is evenly distributed throughout the seitan.
120 g vegetable suet
Remove the seitan from the blender and divide into 4 portions. Roll each portion into a rough cylinder then push all four cylinders together into one fat cylinder.
Place the seitan on a large sheet of muslin or cheesecloth and wrap it very tightly. Tie up the wrapped seitan with chef’s twine or natural string as through it were a regular joint of meat.
Place the seitan joint in a large dutch oven and add all the broth ingredients. Cover with a lid and place in the oven to roast for one hour. After an hour, lift the lid and rotate the seitan so the opposite side is submerged in the broth. Add enough boiling water to top up the broth to half-way up the side of the seitan. Cover with the lid again and roast for another hour.
1 teaspoon black peppercorns, 1 teaspoon mustard seeds, 3 bay leaves, 4 sprigs of fresh thyme, 4 sprigs of rosemary, 1 ½ litres vegetable stock, 1 tablespoon vegan beef stock powder, 3 tablespoon dark soy sauce, 1 teaspoon fine sea salt, 2 teaspoon marmite, 2 tablespoon light brown sugar, 1 head of garlic, 1 onion, 1 carrot, 2 stalks celery
Remove the dutch oven from the oven and carefully remove the seitan. Use scissors to snip the twine and unwrap the muslin. Return the seitan to the broth in the dutch oven. Use a brush to baste the top of the seitan and place back in the oven for a further 20 minutes without the lid.
Serve the seitan sliced thinly with roast potatoes, vegetables and gravy.