Mix the flour, salt, sugar, vanilla sugar and yeast in a bowl. Add the milk, mix and knead into a soft, smooth dough. Knead the butter in well. Cover the dough and leave to rise at room temperature for approx. 2 hr. until double in size.
Divide the dough into six. Press the pieces of dough down lightly and place in the prepared holes. Spread over the jam and mango.
Mix the nuts, sugar and butter with a fork until the mixture turns crumbly, cover the mango with the crumble mixture.
Approx. 25 mins. in the lower half of an oven preheated to 200°C. Remove from the oven, allow to cool a little, then leave to cool completely on a rack. Scatter over the pistachios, dust the crumbles with icing sugar.