Asking around, paging through magazines and newspaper food sections, I found that it was: as a way of assuring even, low heat for cooking, and also for holding delicate foods, such as sauces or creamy mixtures, at a stable temperature.

At one time, the double boiler was an absolute requirement in any home kitchen if only for one task: melting chocolate, which burns very quickly if exposed to direct heat. Though many home cooks switched to the microwave for this purpose, baking experts still favor the double boiler because many microwaves have hot spots which can scorch chocolate. Other popular uses for double boilers are making custards and scrambling eggs to soft, creamy perfection.

Restaurant kitchens often use a double boiler — or its second cousin, the bain-marie or water bath, in which the pot is placed in a larger pan of warm water — to keep standard sauces such as hollandaise warm and stable until needed. To leave the sauce directly on a burner, even on low heat, risks having the sauce overheat and break down into its component parts of solids and liquids, explained Dee Martinez of Kailua, an avid home cook who has worked in restaurants here and on the Mainland.

"For me, the double boiler is like an extra pair of hands in the kitchen. Once you've worked in a restaurant, you realize what a luxury it is to have several cooks working on the same plate. At home, it's only me, trying to time the entree and the starch and the vegetable so that they all come out hot and not overdone at the same time," said Martinez.

She uses the double boiler to hold sauces, mashed potatoes and other creamy starches, cream soups and a hot cheese dip she likes to make. "It allows me to make that dish in advance and keep it warm and moist over barely simmering water while I grill the fish or whatever," she said.

After she read a recipe for double boiler scrambled eggs in the Taste section, Corinne Jonsson of Honolulu called to say she'd read, and successfully used, a technique for making risotto in the double boiler from the 1952 edition of "The Joy of Cooking." (And we thought we'd "discovered" risotto in the 1990s!). "It really surprised me that a double boiler could come so close to helping me make a 'real'-tasting risotto," wrote Jonsson, in a note with which she enclosed a copy of the "Joy of Cooking" recipe.

Joan Osborne of Kailua, subject of a recent Home Cook feature here, uses a double boiler to gently simmer her kama'aina curry sauce over the course of three days, creating a silky texture and perfectly melded flavors.

Or you can make a double boiler for free by fitting a heat-proof bowl (Pyrex, earthenware, metal) into the top of a pot of water. "Joy of Cooking" author Irma S. Rombauer wrote that the ideal is a heavy stoneware bowl that holds heat well, but doesn't heat up too fast. Deep, narrow vessels tend to overheat at the bottom while leaving the top layer too cool, she warned.

It's important that the double boiler top fit snugly into the bottom but sit just above the water line. Many double boilers have a bulge or ridge half-way up the bottom to indicate where the top sits and guide you in filling the pot. The top pot should never sit in the water; this is the same as putting the pot right on the burner.

Always begin by bringing the water in the bottom to a boil, then turning down the heat until the water is gently simmering — tiny bubbles break the surface occasionally. The water should be neither rippling nor still. When using a double boiler for more than 10 or 15 minutes, check water levels and replenish water with boiling water as often as needed. Keep a kettle of water simmering nearby.

If the double boiler gets too hot and food threatens to curdle, boil or scorch, remove the uppermost pot for a few minutes. You may also need to turn down heat under water.

If you're using a bowl as a double boiler top, be sure to handle it with hot pads; the bowl will get very hot.

Never cover the double boiler when you're melting chocolate — condensation dropping into the chocolate would cause it to seize up. Custards also should be cooked without a lid to prevent water from being introduced into the mixture.