First, make the seitan. Blitz the tofu, soy milk, miso, marmite, tarragon, sage, thyme, onion powder, garlic powder, 1 tsp salt and ½ tsp white pepper in a food processor until smooth.
Tip into a bowl and add the wheat gluten and pea protein or protein powder. Mix to form a dough. Once it has come together, give it a really good knead, stretching and tearing for 10-15 mins. It will be ready when the seitan feels springy.
Pour the veg stock into a pan with the onion, garlic and parsley stalks. Bring to a simmer. Flatten out the seitan to 1cm in thickness, and chop into chicken-breast-sized chunks. Simmer these in the stock for 30 mins, covered with a lid. Allow to cool in the stock. Ideally do this the day before and chill in the fridge. These can also be frozen if you wish.
Mix the spice coating ingredients in one bowl. Place the gram flour in another and the plain flour in a third. Mix enough water into the gram flour until it has a texture similar to beaten egg. Dip the seitan pieces in the plain flour, shake off the excess, then coat each piece in the gram flour mixture and finally in the panko spice mix.
In a large frying pan or deep fat fryer, heat the oil to 180C (or until a piece of bread browns in 20 seconds). Once it's hot, carefully drop in the seitan pieces and cook for 6 mins or so, until they are dark golden brown and crispy. Transfer to kitchen paper to drain off the excess oil and sprinkle with a little salt. Serve in toasted buns with salad or slaw, or alternatively as mock chicken dippers with BBQ sauce.