1. To make sauce: saute the garlic and ginger in oil in medium sized saucepan for 30 seconds. Add soy sauce, water, sugar, red pepper flakes, and rice wine; bring to a low boil, boil for 2-3 minutes until sugar is dissolved. Remove from heat and set aside.
2. Combine seitan and 1/4 cup cornstarch in a plastic bag and shake to coat, let sit for 10 minutes. Prepare the yellow onion and bell pepper while waiting. Fry seitan in a few tablespoons of oil until browned, drain on paper towels. Fry the bell pepper and onion until desired softness, add seitan and sauce, bring to boil. Combine 2 tablespoons cornstarch and water, slowly add to sauce (you may not need it all). serve on your choice of rice, and garnish with raw scallions.
Source of recipe: This recipe was modified from this one: http://blogchef.net/mongolian-beef-recipe/ [1]