A double boiler, also called a bain-marie or water bath, sounds like a fancy kitchen gadget, but it is actually easy to make out of basic tools you already have in your kitchen. Use double boilers to melt chocolate, as shown here, and for other recipes, such as Hollandaise sauce or zabaglione.
Choose a large saucepan and a glass or stainless steel bowl that fits snugly over it, covering the entire mouth of the pan, but without touching the bottom of the pan.
Place about 2 to 5cm of water in the pan. Over medium-high heat, bring the water to a gentle simmer, but do not boil.
Too much water?
The water in the pan should never touch the bottom of the bowl overhead. To test the water level, place the bowl over the pan. If you lift the bowl and it is wet on the bottom, pour off a little water.
Place the bowl over the saucepan, and pour the contents to be warmed or melted in the bowl.
Notice any steam?
While melting chocolate, for example, you want to ensure that no steam escapes and touches the chocolate, otherwise it will seize. If you hear that the water is boiling or notice a lot of steam, turn down the heat to low immediately, or briefly move the double boiler off the heat.
Stir constantly with a silicone spatula, whisk or wooden spoon until you've achieved your desired result.