Mix all the "Beef" ingredients together in a food processor until a dough forms. Roll it out slightly with a rolling pin or just pull it with your hands, it does bounce back slightly but just make sure it's flat and not a ball anymore.
Slice seitan in thin strips. They don't all have to be the exact same size.
Whisk together all ingredients for the sauce and pour in a large shallow bowl. Add your strips of seitan to sauce and let sit for 15 minutes. They might stick together slightly but they pull apart easily so don't worry about that.
If serving with rice, start that now.
Prep and chop all your vegetables. I used broccoli, carrots, bell peppers, and onions but feel free to use what you like!
Now, we will cook the seitan. Be sure not to discard sauce. Add 2 tbsps of oil to a large pan on medium-high heat. Lay strips flat on pan, careful not to overlap them. Cook on each side until brown. They cook fast so move quickly. Cook in 2-3 batches, turning heat down as needed, and set aside.
In the same pan, add 1 more tablespoon of oil if needed and cook vegetables of choice. Once vegetables are cooked to your liking, add the ginger beef, and the sauce. Stir until coated, cook for 2-3 more minutes while sauce thickens.
Serve over rice with green onions and sesame seeds for garnish.