The success of many custard recipes (crème brûlée, flan, cheesecake) depends on baking in a water bath, which allows these delicate desserts to cook more evenly and slowly. We’ve always called for adding boiling water to the roasting pan for the bath, but when we were developing our recipe for Lemon Pudding Cakes (see related content), we found that pouring cold water into the pan delivered better results: a bottom pudding layer that was gently and evenly cooked, and a top cake layer that was perfectly baked and nicely browned.
Intrigued, we decided to revisit classic recipes calling for water baths to find out if boiling water was really the ideal. We baked three batches each of crème brûlée (prepared in 4-ounce ramekins) and cheesecake (prepared in a 9-inch springform pan), with three different starting temperatures for the water bath: boiling, room-temperature, and ice-cold. In the baths that started with boiling water, not only did both desserts cook the fastest but these samples had a smoother, more uniform texture. The desserts baked in baths that started with ice water did not cook uniformly; the bottom half was perfectly done while the top half was overcooked. The results weren’t as extreme with baths that started with room-temperature water, but the desserts were still unevenly baked and not satisfactory.
The reason is this: The temperature of boiling water is much closer to the temperature of the oven, which means that the lower portion sitting in the bath and the upper exposed portion start in environments of similar temperature and thus cook evenly. Meanwhile, it will take a bath started with cold or room-temperature water a period of time to heat up, thus slowing the cooking of the submerged portion. While our Lemon Pudding Cakes benefit from this staggered cooking, when it comes to desserts that are one consistency throughout, like crème brûlée and cheesecake, we recommend taking the time to bring a pot of water to a boil for the water bath.
