Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat. Coat seitan with corn starch then add to hot pan. Cook, stirring occasionally, until crispy, 4 to 6 minutes. Stir in the remaining 2 tablespoon oil, onions, garlic and ginger. Cook, stirring often, until fragrant, about 1 minute.
Add mushrooms, cook a few minutes until browned. Add green beans and baby corn or any vegetables of choice. Saute for a minute or so then add the soy sauces to taste. Continue to cook until desired.