A bain-marie is a pan of simmering water that cradles a second vessel holding the food, giving gentle, even heat that never exceeds the boiling point. Named for the alchemist Maria the Jewess, it is indispensable for delicate preparations: melting chocolate without scorching, cooking custards and terrines evenly, and holding sauces at serving temperature without breaking. The water bath buffers against the fierce direct heat of burners and ovens, surrounding the food with uniform warmth. In professional kitchens, the bain-marie also describes the heated counter units that hold prepared dishes during service, though food safety rules limit how long foods may be held this way. The plural is bains-marie, and the technique remains the cook’s answer whenever direct heat would be too harsh.