Rompope (Mexican Eggnog)

Step 1
Bring milk, sugar, and cinnamon sticks to a boil in a large saucepan over low heat. Continue to boil, stirring constantly, until milk has reduced by a little more than one-third, about 20 minutes. Remove from the heat. Leave in the saucepan and allow to cool slightly, about 10 minutes.

Step 2
Beat egg yolks with an electric mixer until thick and pale. Mix in a little of the warm milk mixture. Pour egg yolk mixture into the saucepan with the remaining milk mixture. Stir to combine and bring to a boil over low heat. Stir constantly, scraping the bottom and sides, until mixture is thick enough to coat the back of a spoon, 5 to 7 minutes.

Step 3
Remove from the heat, remove cinnamon sticks, and cool to lukewarm, 15 to 30 minutes. Stir in rum and cool completely, about 2 hours.