Slice ½ the seitan loaf into thin sliced
Combine marinade ingredients and whisk together
Place ingredients in a refrigerator safe container.
Add seitan slices and cover with marinade.
In a large skillet, on medium-low, cook the seitan slices, and add marinade in small amounts throughout the cooking process until all marinade is gone.
In the meantime, saute onions, mushrooms, and peppers.
Heat cheese sauce in a small pan or in the microwave
Toast buns in the oven.
Add a generous amount of seitan to the bun.
Top with onions, mushrooms, and peppers
Drizzle cheese sauce over the top.