Melt 25g butter in a pan and remove from the heat.
Add the milk and crumble in the yeast. Stir until smooth.
Place the flour and salt in a bowl. Make a well in the centre and poor in the milk. Add the egg and mix with a large metal spoon until combined.
Knead for about 10 minutes. It's quite a wet dough but I oiled my work surface rather than flowering it.
Place the dough back in the bowl, cover with a plastic bag and leave in a warm place for an hour or so until doubled in size.
Gathered the dough and rolled into a large rectangle on a floured surface (about 30 x 23 cm).
Melt the remaining 15g butter and brush over the surface.
Mix the sugar, raisins and dark chocolate and spread over the dough, leaving a 1 cm gap around the edges.
Roll the dough up as tightly as possible on the long side. Seal the edges and cut into 12 slices. Place onto a lined baking tray or in my case a 23 cm square silicone mould. Cover and leave in a warm place to rise for another hour or so until doubled in size.
Bake at 190℃ (375℉, Gas 5), for about 30 minutes until golden brown. Warm some honey and brush over the hot buns. Turn out onto a rack to cool.