Our arrowroot comes from the Brazilian cassava plant, which contains high amounts of amyl pectin, a starchy thickener. To thicken sauces and gravies, mix 1 rounded tablespoon arrowroot powder into just a little cool water. Add to 1 cup gravy or other sauce and stir constantly over high heat, about 10-15 minutes. The sauce will thicken suddenly. Once thickening occurs, stop stirring immediately so as not to break down the bonding and thin out the gravy. Ingredients: Arrowroot.