A custard pie is any type of uncooked custard mixture added to an uncooked or partially cooked crust and baked together. In North America, custard pie commonly refers to a plain mixture of milk, eggs, sugar, salt, vanilla extract and sometimes nutmeg combined with a pie crust. It is distinctly different from a cream pie, which contains cooked custard poured into a cooled, precooked crust. Some common custard pies include cheesecake, pumpkin pie, lemon meringue, and pecan pie. True custard is defined as a liquid thickened with eggs. Due to the often large number of whole eggs in custard pie it is a very rich pie.
In 1837, an English chemist named Alfred Bird introduced custard thickened with cornstarch. This became widely known as Bird%27s Custard, but it is not considered true custard because it is thickened with cornstarch. However, this is the main reason Bird’s custard became popular; because there were no eggs used there was no risk for the mixture curdling.
During the 19th century in North America, custards and puddings were marketed as having health benefits. Among those specifically targeted were children and mentally disabled invalids. Ingredients stated to be healthy included tapioca and arrowroot. By the 1930s, instant pudding and custard were widely available to North Americans.
Today, custards are used as filling in pies and tarts, and as individual dishes. Ideally a custard pie should be light and delicate, but still have good body. Custards can be made in two ways: baked or stirred upon the stove, but most custard pie recipes call for baking. The eggs in custard mixtures, when cooked, turn from liquid to solid. If cooked over excessive heat, the eggs will curdle, which is extremely undesirable. Curdling can be prevented by using lower temperatures and stirring. As such, making true custard pie is a very delicate process.