Arrowroot Starch. 

Bob's Red Mill Premium Quality Gluten Free Arrowroot Starch/Flour can be used in gluten free baking for light, delicate textures. Arrowroot is an easily digested starch extracted from the roots of the arrowroot plant, Maranta arundinacea. It is gluten free and can be used as a direct substitute for cornstarch for folks with corn allergies. It has no flavor of its own, so can be used to thicken any sauce, soup, stew, or pudding. For thickening: Arrowroot is best used at the end of your cooking just before boiling, as continued heating will cause it to lose its thickening ability. For gravies and sauces, add arrowroot starch to a small amount of cool liquid first, then whisk into hot liquids. As an egg replacer: Whisk together 1 Tbsp arrowroot starch, 1 Tbsp vegetable oil, and 1/4 cup water to equal one egg. Baking powder substitute: Mix together 1 tsp baking soda, 2 tsp cream of tartar, and 1 tsp arrowroot starch. Store in airtight container.