Start by preparing the TVP by whisking the miso and the stock cube into the boiling water until no more lumps exist, then add the TVP, stir to mix and let it sit for a few minutes until all the liquid has been absorbed. Set aside.
Heat a bit of olive oil in a large frying pan and sauté the onion, garlic, and mushrooms, with a small sprinkling of salt, for about five minutes until the onion turns translucent and the mushrooms have released their liquid. Add the sun dried tomatoes and spinach and sauté for a minute more until the spinach has wilted. Remove from heat and set aside.
In a food processor, process the walnuts until roughly chopped, it takes a few seconds only. Add the prepared TVP, the mushroom mixture, the oregano and paprika, the nutritional yeast, and pepper to taste. Process until well mixed but don’t process it to death – you still want texture. So process a few seconds, scrape down, process a few seconds more, scrape down again, and so on until you have a homogeneous mass. Transfer to a bowl and add gluten flour until you get a consistency that is easy to shape but not too dry. Set aside to rest for 15 to 20 minutes.
Set your oven to 200º C/400º F. Shape your TVP/nut/mushroom mixture into burgers, place them on a baking sheet and brush with a bit of olive oil. Bake for about 30 minutes, gently turning them over after about 20 minutes, until nicely browned on both sides.