Put the flour into a bowl and make a well in the centre. Crumble in the fresh yeast and mix with the 250ml warm milk. Set aside for 15 minutes.
Gradually add the flour from the edge of the bowl mix with the milk and yeast. Add butter, sugar and salt, then knead well till smooth. Place in a greased bowl and cover with cling film. Let rise for 1 hour.
Combine the poppy seeds with the hot milk. Mix in remaining filling ingredients and stir well. Set aside.
Roll out the dough into a rectangle about 5mm thick on a floured work surface. Spread the filling over the dough, allowing a 1 to 2 cm gap along the edges. Roll up lengthways, as you would a Swiss roll. Seal the seam and each end by pressing together with your fingers. Place on a parchment lined baking tray, seam side down. Let rise for 20 minutes.
Preheat oven to 180 C / Gas 4. Bake stollen in preheated oven for 40 minutes. Allow to cool and dust with icing sugar before slicing and serving.