Quick Tip: Bain-Marie

Bain-marie is the French term for water bath, or putting a container of food in a shallow pan of warm water, surrounding it with gentle heat that cooks it gradually. This method is typically used for delicate dishes like custards or mousses so they don't break or curdle.

Egg dishes are often cooked this way, too, as the proteins in eggs become tough and rubbery when cooked at high temperatures.

Use a bain-marie for cheesecakes to prevent the top from cracking in the centre, and custards to prevent a crust from forming before the interior is fully cooked. 

Here's the technique in a nut-shell:
Place your container of food in a shallow pan. Fill the pan with boiling water so it reaches halfway up the dish. (If it hasn't reached a boil, it will take too long for the oven to heat it up.) Place in a moderate oven (like 325 F) and don't cover it.

And that's a bain-marie.