First prepare the seitan. Pour the flour, spices, salt and pepper in a bowl. Pour the water slowly, stirring with a fork first then with your hands for about 15 minutes until dough is rough and elastic. Let the dough rest at least 1 hour.
Put the mixture into a colander and "wash it" under cold running water, kneading constantly. While kneading the water that comes from dough will be white. Continue to knead for about 10 minutes until the water is clear and transparent. At this point the dough will be sticky and rough. Put the dough in a cotton cloth and tie it with kitchen twine.
Prepare a pot with plenty of vegetable broth, add tamari and kombu seaweed. Bring broth to a boil and add the dough wrapped in cotton cloth. Cook for about 30 minutes.
Remove the seitan from the pot and remove the cloth. Pour a little of broth into a bowl, cut the seitan in 12 slices and immerse them in the broth. Set aside and leave to cool completely. You can keep this seitan for about 3 days in refrigerator.
Pour 45 ml olive oil in a pan. Add 15 grams soy butter, 5 sage leaves and 1 crushed clove of garlic. When the butter has melted pour the mushrooms, a pinch of salt and pepper, cover with a lid and cook for about 10 minutes over a low heat. Turn off the heat and set aside.
Take the seitan slices and dry them on absorbent paper. Pour the cornstarch in a bowl, add the sliced seitan and mix well with your hands to cover the slices of starch.
Pour 45 ml of olive oil in a pan. Add 15 grams of soy butter and sage leaves 5. When butter has melted add the sliced seitan in the pan. Cook for 30 seconds on a low heat and then turns all of the slices and cook for another 30 seconds. Pour the white wine, a pinch of salt and sauté for a couple of minutes until the wine turn into a rich creamy sauce. Turn off fire, add the mushrooms, stir with a wooden spoon and serve.