A double boiler is a kitchen tool used for applying gentle heat on the stovetop. It's useful for delicate tasks like making hollandaise sauce, melting chocolate, and preparing custards such as creme anglaise. When cooking these foods, you can use a dedicated double boiler or create one out of a couple of everyday kitchen items.
Why Use a Double Boiler?
The theory behind a double boiler is that you want to heat something in the gentlest manner possible. Some foods are extremely sensitive to heat and standard heating methods—tossing it in a saucepan directly on the burner, for instance—would produce adverse or unintended results. The double boiler produces the slow, indirect heat that these delicate foods require.
For example, when you make hollandaise sauce, you want to warm the egg yolks ever so slightly to improve their ability to form an emulsion. When the yolks are overheated, they'll lose their emulsifying properties. If you really get them too hot, the proteins will curdle, and you'll end up with scrambled eggs.
Similarly, chocolate is an emulsion of cocoa solids, fat, and sugar. When melting chocolate, heating it directly in a pan can affect its texture, turning it thick, lumpy, and dull. Chocolate that is melted slowly in a double boiler is perfectly smooth and shiny, and ready to use in the recipe.
How to Use a Double Boiler
For most stovetop cooking, ingredients go into a pan directly over the heat source. In a double boiler, water is placed in a pot that sits on the burner. On top of the pot, a glass or metal bowl holds the ingredients you're cooking. The steam from the simmering water warms the contents of the bowl every so gently with indirect heat.
When using a double boiler, make sure the bottom of the bowl doesn't come into contact with the simmering water. There should be a gap between the water and the bottom of the bowl. Don't underfill the pot, either. If all the water boils away, you'll just be heating a dry pan, which could damage it.
Create a Double Boiler Setup
You can purchase a dedicated double boiler insert, which is basically a metal colander without any holes. The bowl is tapered so it can fit over many different sizes of pans. The insert also has a handle and spouts to make pouring easier. It's a nice option if you need a double boiler occasionally.
Another option is a double boiler set: A pot and a flat-bottomed insert that fits into it, along with a lid that fits both containers. If you're going to use a double boiler often and have storage space, it's a worthy investment.
Anyone can create a make-shift double boiler using two items in the kitchen. All you need is a pot or large saucepan and a stainless steel or glass bowl that rests on the rim. You might have to experiment with combinations of pans and bowls to find the perfect fit, but it works out nicely for people who rarely use a double boiler.
In a pinch, you can even use a smaller pot that fits into a larger one. It can be an awkward setup since you have to hold the upper pot steady so that it doesn't tilt over, leaving you only one hand for doing everything else.