In a small bowl, whisk together the soy sauce, rice vinegar, hoisin sauce, brown sugar, chili garlic paste, cornstarch, and water. Set the sauce aside.
Heat 1 tablespoon of oil in a large skillet or wok over medium-high heat. Add the seitan chunks and cook for 5-6 minutes, turning occasionally, until browned on several sides. Remove and set aside.
Add the remaining oil to the pan. Add the bell pepper and dried chilies and stir-fry for 2-3 minutes until the pepper begins to soften.
Add the garlic and ginger and stir-fry for 30 seconds until fragrant.
Return the seitan to the pan. Give the sauce a quick stir and pour it in, tossing everything together until the sauce thickens and coats the seitan, about 1-2 minutes.
Stir in the peanuts and sliced scallions and toss to combine.
Serve hot over rice, garnished with extra scallions.
