Bain-Marie: A Water Bath
A water bath is a technique used for cooking egg custards, some cheesecake recipes and delicate dishes like mousses.
The method, called bain-marie in French, prevents these dishes from cracking or curdling during baking.
To cook using a water bath, place the cooking container, i.e. custard cups, souffle dish, etc., in a larger container partially filled with hot water.
The water will insulate the food from the direct heat of the oven by surrounding it with even, gentle heat.
Here are a few things to remember when using a bain-marie ~
Your outer container should be deep enough to hold water at least 1/2 to 2/3 the depth of your cooking container.
Place a cake cooling rack or a thick folded towel in the bottom of the outer container to be sure that the water flows underneath the food, too.
If at all possible, add the hot water to the pan after you've placed it in the oven. This avoids the possibility of sloshing it over the top of your food when moving the pan.
Be sure to remove your food from the water bath as soon as cooking is complete. If left in the hot water, it will continue to cook.
From MyGourmetConnection How To Cook ~ Cooking Tips