1. Boil the orange whole for 45 minutes,then quarter and remove the seeds and central membrane,leaving the peel on. Blitz with the ginger in a blender until smooth;you'll need about 220g of puree.
2. For the sugar syrup,heat the sugar and water in a small saucepan until the sugar dissolves,then set aside to cool.
3. Dissolve the yeast in the warm water and set aside for 5 minutes to activate.
4. Place the flours,butter,sugar,mixed spice,cocoa,salt,orange essence and the orange and ginger puree in a stand mixer. Combine on a medium speed with the dough hook,pouring in the yeasted water. Mix for 10 minutes until a soft,smooth dough forms. Add the chocolate buttons and mix for a couple of minutes to combine. Tip the dough onto a bench and rest for 20 minutes.
5. Once rested,divide the dough into 12 even pieces and roll into balls. Place on a lined baking tray about 2-3cm apart,cover with a tea towel and set aside for 2-3 hours until they've doubled in size.
6. When ready to bake,preheat oven to 220C fan-forced (240C conventional).
7. To make the crosses,combine the ingredients in a bowl,then transfer to a piping bag with a small (about 5mm) plain nozzle. Pipe crosses onto the buns,then bake for about 25 minutes until risen and coloured.
8. Brush the buns with sugar syrup as soon as they come out of the oven,then set them aside to cool a little before eating while still warm. To reheat buns,toast them or warm in the oven.
Serving suggestion: I also love these buns toasted,with that little bit of extra crunch,again with the butter barely managing to hold its form as it slips into the bun.