You're trying to prepare a recipe, and suddenly you realize it calls for a double boiler ... and you don't have one. Maybe you're not even entirely sure what it is. Don't sweat it.
While nobody seems to compile statistics to back this up, it's a safe bet that the majority of home cooks don't own a double boiler. Its uses are few and specialized, and you can easily mimic the effects of one with other stuff you have in your kitchen.
What Is a Double Boiler?
Basically, a double boiler is just two cooking pots. One goes on top, on the rim of the other, leaving a cavern of empty space in the lower pot. With some models, one pot is shallower than the other, and it sits on top of the bottom one, dipping down into it a little but still leaving empty space between them.
You put an inch or two of water in the lower pot, which sits on the burner. Then you bring the water to a boil, and then turn the heat down to low. Ingredients that require particularly gentle heating go into the top pot – which can't be allowed to touch the water – and it heats slowly and evenly.
What Are Double Boilers Used For?
Some ingredients and preparations need to be heated gently and gradually without coming into direct contact with the heat source. Otherwise, they burn, separate, seize, curdle, clump or otherwise get ruined.
Melting chocolate is the most common use for a double boiler. Chocolate is highly heat sensitive, easily scorching when in direct contact with a heat source. If it gets too hot too fast, it can also seize up, turning quickly from a smooth liquid into an unappealing thick, clumpy paste.
Some egg emulsion sauces like Hollandaise are made in a double boiler too. Most basic custards, like crème anglaise, are also prepared in one.
How to Make Your Own DIY Double Boiler
If a recipe calls for a double boiler, don't try to do without it – you will fail. But you don't have to run out to the store, because you can just make your own. To create the effect of a double boiler, all you need is two pots, or one pot and a slightly larger heatproof bowl. What's a heatproof bowl? Any kitchen-grade metal, glass or ceramic bowl will do.
One pot goes on the burner. The top pot or bowl must sit on the rim of the lower pot with enough room so that it does not come into contact with the inch or two of water underneath (even if the water is boiling). The top pot or bowl should also seal off the lower pot to hold in all the steam generated by the heated water.
Bring 1 to 2 inches of water to a boil in the lower pot before introducing the top pot or bowl. Then, turn the heat down to low and put the top vessel on. Then put the ingredients into it. Many double boiler preparations require constant or near-constant stirring as soon as they begin to heat up, so read through the recipe to know what to do as soon as the ingredients are in your makeshift double boiler.
Again, the top vessel should never be touched by the water in the bottom pot. Don't let the water reach a boil once the ingredients are in the top pot or bowl; it should stay at a simmer. The top vessel will get hot, so if it doesn't have a handle, use potholders to move it when you're done.
Should You Buy a Double Boiler?
As you can see, it's very simple to get the effects of a double boiler with items you already have on hand. So there's really no need to spend the money on a double boiler and sacrifice the storage space in your kitchen. But if you like collecting kitchen gadgets and frequently melt chocolate, make eggs Benedict or prepare French sauces, it's a useful item – so it's your call.