A double boiler is used for cooking foods gently on the stovetop. Made up of two nesting saucepans, double boilers are available in cookware stores, but a makeshift one is easy to assemble. Choose a saucepan and a heatproof bowl that rests securely in the top of the pan. Fill the saucepan with water to a depth of 1 to 2 inches. Once the bowl is placed atop the pan, the water must not touch the bowl; allow at least 2 inches of clearance. Bring the water to a boil, set the bowl in place, and reduce the heat so that the water simmers gently.