A classic vanilla custard is good... but a sweet and slightly spiced one infused with the flavours of chai is better.
Heat the milk in a saucepan with the chai teabags until just simmering, then leave to one side for 5 minutes before scooping out the bags.
Separate the eggs and whisk the yolks in a bowl with the caster sugar and cornflour.
Pour the infused hot milk onto the egg yolk mixture as you whisk. Return to the saucepan and cook gently, stirring continuously, until it thickens. Cool to use.