Make the crust: blend together the coconut sugar, smoked paprika, ground pepper, ground coriander, garlic and onion powders, Marmite and tahini.
Lay pieces of aluminium foil (one for each piece of seitan) and cover with crust. Transfer each piece of seitan to pieces of foil, flipping over to coat completely. Roll as tightly as possible.
Bake each seitan piece, tightly wrapped for 45 minutes at 180°C.
Take out of the oven, leave to cool down, open each wrap and bake again, uncovered, for 30 minutes, or until each piece has blackened.
Leave to cool down again and get the broth ready.
Cut each piece of seitan into slices, and boil for 5 minutes into the broth if using immediately (ici avec des bagels au curry), or keep refrigerated in the broth.