Microwave Custard

2 egg yolks
2 heaped tablespoons cornflour

1 teaspoon vanilla essence
2 cups milk
2 tablespoons caster sugar
1.      Whisk egg yolks, cornflour and vanilla to a smooth paste with a tablespoon of the milk.
2.      Place remaining milk and caster sugar in a separate microwave bowl. I use a clear Pyrex 4 cup jug. That way I can see through the window when it boils and the jug is big enough for it to not boil over.
3.      Heat milk in microwave until it boils. This takes 5 minutes in my microwave, but will be different in yours. It must boil or the custard will not thicken.
4.      Remove from microwave and pour into the egg yolk mixture, whisking as you do this.
5.      Whisk until thick.