Preheat the oven to 350 and lightly spray an 8x8 baking dish with canola oil. Mix the first 3 ingredients together in a large bowl. Mix the water with the peanut butter, sesame oil, soy sauce, garlic, and ginger and add it to the dry ingredients. Stir to mix well and then knead lightly for a couple of minutes.
Put the dough into the baking dish and flatten it so that it evenly fills the pan. Take a sharp knife and cut it into 8 strips; then turn the pan and cut those strips in half to form 16 pieces.
Put it in the oven and bake for 20 minutes. While it's baking, prepare the sauce, below. After 20 minutes, pour half of the sauce over the top of the seitan, spreading it to cover completely, and return the seitan to the oven. Cook for 10-15 minutes. Remove from oven and cut apart to serve.
Sauce
Spray the bottom of a non-stick sauce pan lightly with canola oil and heat over medium-high heat. Add the garlic and ginger and cook for about 2 minutes. Add all remaining ingredients except the cornstarch and broth and heat until boiling.
Mix the cornstarch with the vegetable broth until smooth and stir it into the sauce. Cook, stirring, until mixture thickens. Keep warm on lowest heat until needed.
http://blog.fatfreevegan.com/2007/05/seitan-baked-in-sweet-and-sour-orange.html