This recipe is both easy to make and very tasty. Adapted from Larousse Gastronomique. The custard is pourable, but noticeably thickened (similar to yoghurt).
The amount of sugar gives it a reasonably sweet taste, but the original recipe is even sweeter, so adjust to taste :) You can use powdered sugar, but it's not absolutely necessary, the sugar will dissolve quite nicely in the milk. Cane sugar can also be used, but be sure to use a bit less of it.
You can also use an extra egg yolk (instead of the corn starch).