After making the hot cross buns following this method - http://sourdough.com/forum/sourdough-hot-cross-buns  I've been experimenting with a few different ingredients. My latest effort is the best yet, I left out the nutmeg and allspice and 20g or so of the flour and added the same amount of cacao powder in. I also grated a 100g block of 85% cocoa chocolate and added that in.
I baked them this morning after an overnight stint in the fridge and they turned out beautifully, they are so delicious.
I'll see if I can attach a photo.