• Pre-heat your oven to 180°C (350°F/gas mark 4).
• In a large mixing bowl, mix together the vital wheat gluten, nutritional yeast, bouillon powder, paprika, rosemary, and black pepper.
• Using a blender (counter-top or immersion), blitz the garlic, stock, oil, and Marmite together, and then add to the dry ingredients.
• Mix well until everything is incorporated, and then knead for five minutes. (note 1) 
• On a large piece of silicone baking parchment, roll out the seitan into a vaguely rectangular shape, until it's around 1.5cm (½") thick.
• Spread liberally with the pumpkin purée, and then add a layer of the cabbage and mushroom stuffing.
• Using the baking parchment, and starting at one of the short ends, carefully roll the seitan up into a log shape. Try not to stretch the seitan as you do this. Press the ends of the seitan together to seal.
• Tightly wrap the log in aluminium foil. If your foil is thin, use two or three layers.

  (I wrap mine up like a giant toffee - and tightly twist the ends of the foil to stop it coming undone!)
• Place the seitan directly onto a shelf in the centre of the oven, and cook for two hours, turning it over every 30 minutes, to ensure even cooking and browning.
• Once it's cooked, allow the stuffed seitan roast to rest in its wrapping for 20 minutes before slicing.
• Serve with traditional roast veggies, make-ahead mushroom gravy, and any other trimmings you fancy.

To store:

• Keep the vegan stuffed seitan roast in the 'fridge, wrapped in tin foil, for up to two weeks. Reheat in a low oven, or fry slices in a few sprays of sunflower oil.
• This roast can also be frozen for up to three months: defrost thoroughly, and reheat as before.