0 a device or a process for cooking foods that involves putting the food in a container into a pan of hot water: --
In a very traditional form of terrine, "au torchon" (in a towel), a whole lobe of foie is molded, wrapped in a towel and slow-cooked in a "bain-marie".
Usually it is cooked together on the stovetop, but other methods exist including microwaving, steaming, baking (sometimes in a bain-marie) or freezing (using gelatin as a thickener).
A custard is made using milk, sugar, vanilla, and egg yolks; the mix is cooked in a bain-marie for a few minutes, but must remain thin enough to pour.
Under the outer container of the bain-marie (or built into its base) is a heat source.
The most common preparation is a "bain-marie" method where a reduction of vinegar is used to acidify the yolks.
It is usually cooked in a bain-marie on a stove top or in the oven in a water bath.
A second, modern usage, for the term porringer is a double saucepan similar to a bain-marie used for cooking porridge.
Thick celluloid panels are cooked in a bain-marie which turns them into leather like substance.