Dissolve 1 teaspoon sugar and yeast in lukewarm milk and leave for 10 minutes. A yeast foam forms on the milk.
Sieve the flour and mix with the salt, sugar and vanilla sugar.
Wash the orange well, grate the zest and add to the flour.
With a dough hook: Add the yeast-milk mixture to the flour and knead.
Gradually knead in the egg, then the butter by the teaspoonful.
Knead the dough for 20 minutes with the dough hook.
Grease a large bowl with a little oil and let the kneaded dough rise in it, covered, for about 4 hours in a warm place.
Syrup
Squeeze the grated orange and run the juice through a fine sieve. Alternatively, you can use ready-made orange juice from the supermarket.
Put the orange juice with the sugar and orange flower water into a saucepan and bring to the boil while stirring.
Stir until the sugar has dissolved. Then remove from the heat and leave to cool.
Filling
Roast the hazelnuts in a pan and set aside to cool. Then chop coarsely.
Melt the chocolate and butter in a pan on a low heat and mix well. Sieve the icing sugar and stir in.
Fill and knot the babka
Turn the dough out onto a lightly floured work surface and roll out into a rectangle about the thickness of a finger.
Spread the chocolate cream on the rectangle about 5 cm from all edges and spread the hazelnuts on top.
Now carefully roll up the rectangle from the longer side. The result is a filled dough snake.
Cut the dough snake lengthwise in the middle with a sharp knife. You now have two long pieces of dough, each with a cut surface where you can see the filling.
Place the dough pieces crosswise with the cut surface facing upwards and place the dough pieces on top and bottom one after the other until a plait is formed.
Grease the loaf tin with a little oil and place the plait in it. The plait will probably be longer than the tin. This is normal. Carefully compress the plait into the mould.
Leave the babka plait to rise in the loaf tin for another 90 minutes.
Preheat the oven to 190 °C.
Bake the cake for about 30 minutes and then pour the syrup directly over the babka while it is still hot.
Allow the babka to cool completely and then turn it out of the mould.
The babka you can cut into about 12 pieces. In a tin or paper bag is durable for about 4 days.