For the Eierlikörstriezel, mix the eggnog, yeast, sugar, vanilla sugar, lemon juice, rum and most of the ice cream.
Set aside a small portion of the egg whites, for brushing. Add flour to the mixture, add the butter and knead until a firm dough is formed.
Let the dough rise, covered in a warm place, for 1 hour. Form 6 balls from the dough and let rest for another 15 minutes.
Form strands of equal length from the balls (about 30 cm) and braid 3 strands each into a Striezel. Leave to rise for a further 40 minutes.
Brush the Striezel with the egg white and bake in a preheated oven at 170 °C for 25-30 minutes until golden brown.