What is the process called when you slow cook an egg mixture over a double boiler?

The process of slow-cooking an egg mixture over a double boiler is called "tempering".

Tempering refers to the gentle heating of an egg mixture to prevent it from curdling. Here's why it works:

* Double boiler: The steam from the lower pot gently warms the egg mixture in the upper pot, preventing direct heat contact.

* Gradual heating: This slow, indirect heating allows the egg proteins to gradually denature and thicken without becoming grainy or rubbery.

Tempering is commonly used to make custards, sauces, and hollandaise sauce.