Crème anglaise
Crème anglaise is a pouring custard of milk or cream, egg yolks and sugar, cooked until lightly thickened. There is no starch in it: the structure comes from the yolk setting as it heats.
The mixture is cooked over low heat, stirred constantly, to around 82–84 °C. Below that the custard stays too thin; above it the yolk curdles into flecks and the custard splits. The classic test without a thermometer: the custard should coat the spatula well enough that a finger drawn through leaves a clean line.
Anglaise works both as a sauce in its own right and as a base for a great deal else: bavarois, crémeux, ice cream and a number of mousses are built on it. Once cooked it is strained and chilled at once, or residual heat carries on cooking it.