NOTE: This recipe needs uncooked seitan. Cut the seitan into four thin pieces ( 0.125 to 1 cm thick), each about 2 ounces. The thinner the better. Fry the seitan in a (little?) hot oil until lightly browned and then simmer it in a little water for about 30 minutes before using. If you don't simmer it first, you may need to add more liquid to the recipe. Saute the onions and garlic in the oil until the onions are soft and translucent but not fully cooked. Place the seitan in an ovenproof baking dish and cover it with tamari, apple juice concentrate, and water. Cover with the sauteed onion mixture and sprinkle the ground pecans over it, if you wish. Fan the apples over the onions and pour the mirin on top. Cover the dish with a tight-fitting lid or aluminum foil, and bake at 150ºC for 2 hours. Serve hot.