Combine the flour, salt, sugar and castor sugar.
Rub in the butter.
In a jug, combine the Milo, yeast and egg. Mix well.
Add the Milo mixture to the flour and combine to make a soft dough.
Turn out onto a clean work surface and knead for at least two minutes. (five is preferred)
Place the kneaded dough into a clean bowl and cover with a dish towel or clingfilm. Allow to prove for at 45 minutes. Start 45min timer
Turn the dough out onto a work surface and knead for another minute.
Roll out into a rectangle and grate chocolate over the rolled out dough. Place any small, leftover chocolate into the dough.
Roll up the dough from the long edge, taking care to roll tightly.
Fold the ends of the rolled-up dough under and place in a greased loaf tin.
Allow the dough to prove for another 45 minutes. Start 45min timer
Preheat the oven to 200ºC. Place the loaf into the oven and bake for 15minutes. Start 15min timer
Turn the temperature down to 180º and bake for a further 30 minutes. Start 30min timer
Remove the bread from the tin and allow to cool on a wire rack for about 10 minutes before cutting and serving.