Custard preparation is a delicate operation because a temperature increase of 3–6 °C (5.4–10.8 °F) leads to overcooking and curdling.

[1] A bain marie water bath slows heat transfer and makes it easier to remove the custard from the oven before it curdles.

[2] Adding a small amount of cornflour (U.S. corn starch) to the egg-sugar mixture stabilises the resulting custard, allowing it to be cooked in a single pan as well as in a double-boiler.

When starch is added, the result is called 'pastry cream' (French: crème pâtissière, pronounced [kʁɛm pɑtisjɛːʁ]) or confectioners' custard, made with a combination of milk or cream, egg yolks, fine sugar, flour or some other starch, and usually a flavoring such as vanilla, chocolate, or lemon.

Crème pâtissière is a key ingredient in many French desserts, including mille-feuille (or Napoleons) and filled tarts.

Some kinds of timbale or vegetable loaf are made of a custard base mixed with chopped savoury ingredients.

Bougatsa is a Greek breakfast pastry whose sweet version consists of semolina custard filling between layers of phyllo.

Custard may also be used as a top layer in gratins, such as the South African bobotie and many Balkan versions of moussaka.

[9] Examples include Crustardes of flessh and Crustade, in the 14th century English collection The Forme of Cury.

[12][13] In modern times, the name 'custard' is sometimes applied to starch-thickened preparations like blancmange and Bird's Custard powder.