Bain-marie is a fancy French term for a hot water bath. It is used to make custards and melt chocolate. To make a bain-marie, pour 3 inches/8 cm of water in a saucepan, then place a heatproof bowl (another pot or a glass Pyrex bowl) on top of the pan. Ensure that the top bowl fits snugly over the saucepan so the steam is trapped beneath it. Bring the water to a simmer, place ingredients into the top pan, and follow the recipe's instructions.