Note- The prep time includes 1- 1½ hours of proving.
Place sultanas and currants in a bowl and pour hot water over them, sit for 15 minutes, then drain, discarding water.
Add yeast and 1 teaspoon of the maple syrup to the warm milk, mix well and set aside for 6-10 minutes until foaming. Stir in the oil, egg and remaining maple syrup.
Place the flours, spices and salt in a large mixing bowl. Stir to combine. Add soaked fruit, yeast mixture and chocolate. Mix well and turn out onto a lightly floured surface, knead gently until dough is smooth. Mixture will be quite sticky to start with, use clean hands if too sticky.
Place dough into a clean, lightly oiled bowl and cover with plastic wrap. Sit in a warm place, allowing dough to double in size. This may take anywhere from 30-60 minutes.
Tip risen dough onto a lightly floured surface and knock back. Divide into 6 even sized portions. Roll each piece into a smooth ball and place into a lightly floured baking tray approx. 2-3cm apart. Cover loosely with a tea-towel and allow to rise until the balls have almost doubled in size and are touching. Pre-heat oven to 220°C (200°C fan-forced).
For the crosses, whisk together the flour and enough water until a thick smooth paste has formed. Spoon into a piping bag and pipe over the risen buns. Bake for 10 minutes, then reduce heat to 200°C and cook a further 10 minutes.
Whilst still warm, brush the combined maple syrup and mixed spice over each bun. Allow to cool slightly before enjoying.