Step 1: Slice the seitan into bite-sized pieces. Mince the garlic and grate the ginger. In a small bowl, whisk together the soy sauce, rice vinegar, maple syrup, sesame oil, and cornstarch until smooth. This is your easy seitan teriyaki sauce.
Step 2: Heat the neutral oil in a large non-stick skillet or wok over medium-high heat. Add the sliced seitan and sear for 3-4 minutes per side, until golden brown and slightly crispy. Remove the seitan from the pan and set aside.
Step 3: Reduce the heat to medium. Add the minced garlic and grated ginger to the pan and sauté for 30-60 seconds until fragrant. Be careful not to burn the garlic.
Step 4: Pour the whisked teriyaki sauce mixture into the pan. Bring to a gentle simmer, stirring constantly, until the sauce thickens and becomes glossy, about 1-2 minutes. This thickened glaze is key to a perfect easy seitan teriyaki.
Step 5: Return the cooked seitan to the pan. Toss gently to coat all the seitan pieces evenly with the thickened teriyaki sauce. Cook for another 1-2 minutes, allowing the seitan to heat through and absorb the flavors of the easy seitan teriyaki.
Step 6: Remove from heat. Garnish with toasted sesame seeds and chopped green onions, if desired. Serve your incredible easy seitan teriyaki immediately over rice or noodles.