Egg Grog from the North of Germany

During the Christmas days and mediocre weather lets you serve the channels on the TV.
I watched a series about the northern islands along the North Sea.

A man in Eckernfoerde has a restaurant and offers tour groups a course in preparing the Egg Grog.
Grog is just rum, sugar and hot water.

To give it a very creamy finish, use an egg yolk.

But now the work starts. Put the egg yolk in a heat proof glass and add the sugar. Use a teaspoon and start stirring until you have a white thick creamy paste. That takes a lot of elbow grease and takes about 20 min. Or you use such a spiral tool andvthen it takes about 6 min.

When the egg mix is the right consistency, pour 8 cl brown rum and 150 ml hot water on top.

Per Person:
1 egg yolk
1 tbsp sugar
8 cl brown rum
150 ml hot water