Mexican Eggnog

Start by heating milk, sugar, and cinnamon sticks in a large saucepan over low heat. Keep the mixture simmering, stirring frequently, until it has thickened noticeably and reduced by nearly two-thirds, approximately 20 minutes. Take the saucepan off the heat source.

Allow the mixture to sit undisturbed for a short while, giving it time to cool down slightly, roughly 10 minutes.

Next, whisk egg yolks in a separate bowl using an electric mixer until they become light and fluffy. Gradually add a small amount of the warm milk mixture to the egg yolks, mixing well.

Carefully pour the egg yolk mixture into the saucepan with the remaining milk mixture. Combine everything thoroughly, then bring the mixture to a boil over low heat once more. Stir constantly, making sure to scrape the bottom and sides of the saucepan, until the mixture has thickened sufficiently to coat the back of a spoon, taking anywhere from 5 to 7 minutes.

Remove the saucepan from the heat source and discard the cinnamon sticks. Let it sit at room temperature for a longer period of time, around 15 to 30 minutes.

Finally, stir in the rum and let it cool down completely, taking roughly two hours to reach this stage.