Custards are a broad family of soft egg-and-milk dishes. They may be baked, boiled or steamed, either in cups or one large dish. A British person talking about "custard" is referring to what other people might call crème anglaise.
The usual rule for custards is about eight eggs to 1 liter (approximately 1 quart) of milk; but a very good custard can be made of six, or even fewer, especially with the addition of a level tablespoonful of sifted flour, thoroughly blended in the sugar first, before adding the other ingredients. It improves custard to first boil the milk and then cool it before being used; also a little salt adds to the flavor. A very small lump of butter may also be added, if one wants something especially rich.
To make custards look and taste better, duck's eggs should be used when obtainable; they add very much to the flavor and richness, and so many are not required as of ordinary eggs, four duck's eggs to the pint of milk making a delicious custard. When desired extremely rich and good, cream should be substituted for the milk, and double the quantity of eggs used to those mentioned, omitting the whites.
Eggs should always be thoroughly well beaten separately, the yolks first, then the sugar added, beat again, then add the beaten whites with the flavoring, then the (sometimes cooled) scalded milk. The lighter the eggs are beaten, the thicker and richer the custard.