The key to this recipe is to thinly slice the mushrooms, peppers, and onions. The mushrooms, after they cook, should take on the shape of thinly sliced steak. Also, you want to toast the roll with a little butter on it. Personally, I think it gives it a much more authentic hoagie or hot sub taste. Trust me and just get the butter out. When all is said and done you will feel like you are chowing down on a super unhealthy hoagie! But you're not!