Confectioner's Custard, we used to call it when I was a kid. I love it!
2 eggs
50g vanilla sugar (or 2 drops vanilla extract added to caster sugar)
2 tbsp flour
300ml milk
30g unsalted butter
Blend together the eggs, sugar and flour until smooth and fluffy. Meanwhile, bring the milk to a boil then take off the heat and add to the egg mixture, stirring continuously. Return the mixture to the pan, return to a boil, then remove from the heat and add the butter.
Cover the mixture with a circle the same size as the pan and set aside until cold before using.