In a medium bowl, whisk the egg yolks and sugar until pale and thick.

In a saucepan, heat the milk, cream, nutmeg and cinnamon over medium heat until steaming. Do not let it boil.

Slowly pour about half of the hot milk into the yolks, whisking constantly, to temper them.

Pour the mixture back into the saucepan. Cook over low heat, stirring constantly, for 3–5 minutes, until it coats the back of a spoon or reaches 160°F.

Remove from the heat and stir in the vanilla, and the rum if using. Strain into a pitcher.

Serve warm, or chill for at least 2 hours. Top with extra nutmeg.