Mix the butter, icing sugar, vanilla sugar, egg yolks, rum and a pinch of salt well with a hand mixer or food processor. Then stir in the two types of flour and the baking powder and knead everything into a smooth dough.
Wrap the dough in cling film and leave to rest in the refrigerator for at least 40 minutes.
Preheat the oven to 170°C top/bottom heat.
Roll out the dough on a floured work surface to a thickness of approx. 3-4 mm.
Line two baking trays with baking paper or a baking mat.
Cut circles out of the dough and place them on the baking trays. Knead the leftover dough again, roll it out and cut out more circles.
Bake the biscuits for approx. 14 minutes. They should remain light in colour and not brown.
Allow the biscuits to cool. In the meantime, place the caramel cream and coconut flakes in a shallow bowl.
Spread a thick layer of dulce de leche on one biscuit, place a second biscuit on top and press down gently. The caramel cream should ooze out slightly at the sides.
Roll the biscuits with the caramel edge in the coconut flakes.
Store in a cool place so that the dulce de leche does not leak out of the alfajores.
