You don't have to use truffle oil but it gives it a wonderful earthy taste. Don't use to much or it will over power the dish. I am always trying to find different side dishes to serve and this is a great choice to mix things up.
Place truffle oil in large skillet. Saute onions, garlic and mushrooms until mushrooms are browned. If you need a little more oil add olive oil. Stir in quinoa. Cook a couple of minutes. Stir in tomatoes and season with salt and pepper.