Combine the egg yolks and evaporated milk in a large bowl.
Slice the vanilla pod into half and scrape the vanilla seeds out with the back of the blade of the knife, add the seeds to the mixture and stir (do not whisk) until well combined.
Add the sugar and then keep on stirring until the sugar is dissolved. This might take a while.
To get a smoother texture, use a sieve while transferring the mixture into another bowl.
Lastly, add the brandy and stir a few times more.
Transfer the Eierlikör or Eggnog in bottles and let it stay overnight in the fridge if you can wait.
Notes
This recipe makes 2 liters of Eierlikör or Eggnog. The original recipe calls for Cognac (brandy) but rum can be used instead.