Start with a #30003 Gluten Free Hamburger Bun. While grilling your hamburger patties, sauté mushrooms and thinly sliced onions in a pan with butter. Place finished burgers on the toasted gluten free buns, and divide the mushroom-onion mixture evenly over the burgers. Top with gluten free condiments, if desired. You won’t believe this crowd pleasing classic is also gluten free!