Mix the flour and 625ml/21fl oz water together in a very large bowl to form a dough. Knead by hand or use electric dough hooks until it is supple and elastic, and doesn’t break when stretched to the point you can see light through it. If doing by hand, this will take around 15 minutes. Clean the bowl out and place the dough back in the middle. Cover with cold water and leave to rest for at least 1 hour, or up to 2 hours.
Drain the water and rinse the dough well under the tap for 5 minutes, or until most of the starch has been removed and the water runs fairly clear. The dough will look stringy and a bit like a sponge at this point. Put it back in the bowl, cover with a cloth, and rest for a further 1 hour.
Knead the paprika, salt and pepper into the dough until well-combined.
Heat 1 tablespoon of oil in a large frying pan over a medium heat. Cut off strips of the dough and fry on each side until golden brown, adding more oil if needed. You may have to do this in two batches. Remove from the heat, add all the seitan strips and carefully pour in the stock, being careful as the oil may spit. Cover with a lid and simmer over a low heat for 15-20 minutes, making sure to top up the liquid a little if it starts to boil dry. Set aside to cool.
Meanwhile, mix the dry coating ingredients together in a bowl and beat the egg in another bowl. When the seitan strips have cooled, dip each into the egg, then the seasoned flour, and repeat once more.
Heat 1 tablespoon of oil in a frying pan and fry the seitan strips on both sides until golden brown.