600ml whole milk
6 large free-range egg yolks
2 tbsp vanilla caster sugar (or use caster sugar and add a tiny drop of vanilla extract)
1 tsp plain flour
1. Heat the milk to scalding point in a heavy-based saucepan. Meanwhile, in a bowl, beat the egg yolks with the vanilla caster sugar and flour until pale and smooth. Pour the milk over the egg mixture, whisking until mixed well. Now return the mixture to the milk pan and reheat it very gently, stirring all the time (a wooden spoon or spatula is best). As soon as the mixture begins to coat the back of the spoon, rather than just looking like hot milk, the custard is ready. It shouldn’t be any thicker than, say, single cream. Easy eh?
2. Serve immediately for best results, or keep it warmish, rather than reheating, if you are making it ahead.