A bain marie is a double walled saucepan designed to keep food warm or heat gently cooked food from below. There are two main types of bains marie used in commercial kitchens - dry well and wet well. A dry well bain marie heats the air underneath the pan by using an electric element. A wet well bain marie relies on hot water to heat the food.
Bains marie are very useful for holding and storing pre cooked foods, sauces, fillings, curries, soups and gravy at a constant temperature; a built in thermostat on most models ensures the temperature is consistent and therefore keeps the food at a safe temperature.
Fill wet well bains marie with boiling hot water as this saves time and energy.