Mix egg yolks and bourbon vanilla sugar in a metal bowl. Gradually stir in icing sugar, condensed milk and rum. Whisk with the whisk of the mixer in a hot water bath for about 6 minutes until thick and creamy.
Fill egg liqueur into wide bottles. The liqueur keeps well closed in the refrigerator for about 4 weeks.
Coconut egg liqueur: From the basic recipe replace the condensed milk with 1 can (400 ml) of unsweetened coconut milk. The coconut egg liqueur is thicker than the basic recipe. It is therefore essential that you fill it in a bottle with a wide neck.
Before serving, dip briefly into hot water or add 1-2 tablespoons of rum or milk, then shake vigorously.
Chocolate egg liqueur: For the chocolate syrup boil 200 ml water and 200 g sugar. Stir in 80 g cocoa and simmer for about 5 minutes. Season with 1 skewer each of cardamom and cinnamon and let it cool down lukewarm.
From the basic recipe replace the icing sugar with chocolate syrup and the condensed milk with 300 g whipped cream.