A double boiler is a stovetop apparatus used to cook delicate sauces such as beurre blanc or to melt chocolate without burning or seizing. It is a double-decker saucepan with an upper vessel that fits into a lower pot.

One fills the bottom with boiling water and places the food to be cooked in the top one. The top pot is kept above the boiling water and heated only by steam, but tight fitting of the two pots prevents steam from escaping.

A normal saucepan can be used instead if you do not have a double boiler!