How to cook
Separate the egg whites from the egg yolks. Beat the yolks to a froth along with half of the sugar.
Mix the rest of the sugar with the milk and coffee. Boil the mixture for a few seconds, then remove it from the heat. While stirring constantly, add in the yolks.
Place the mixture back onto the hob and cook over very low heat, while being careful not to boil it. When the mixture thickens, remove it from the heat, pour it into a suitable container and place it in ice to cool down. Add the liqueur to the cooled mixture, stir and store it in the freezer for 2-3 hours.
Once the mixture has set, take it out from the freezer, beat it with a mixer and store it in the refrigerator or freezer until it's time to serve it.