Line 2 trays with unbleached baking paper
Combine the flours and baking powder in a small bowl
In a separate large bowl, beat together the butter and sugar with electric beaters until pale and creamy - around 2 minutes
Beat in the egg, vanilla, orange juice and zest, then fold in the flour mixture until just combined
Pop the dough into the fridge for 20-30 minutes
Preheat the oven to 180 degrees fan forced
Roll 1 heaped tablespoon of mixture at a time into balls, place on tray and flatten biscuits lightly. I fit 9 on each tray evenly spaced out.
Bake for approx 15 minutes or until the biscuits are lightly golden, then allow to cool on tray for 5 minutes before removing to a wire rack to cool completely.
While biscuits are cooling melt dark chocolate in a small saucepan on very low heat (or use bain marie method), stirring frequently. Dip one side of the cooled biscuits into the melted chocolate then place back onto the wire rack until chocolate sets.
Store in air tight jar for up to a week. Can be frozen.