1. Line two baking trays with baking paper. Chop chocolate into chunks, set aside. In a medium bowl, sift together flour, ground ginger,cinnamon, mixed spice, and cocoa.
2. In the bowl of an electric mixer, beat butter and grated ginger until whitened, approx 4 minutes. Add brown sugar, beat until combined. Add golden syrup, beat until combined.
3. In a small bowl, dissolve bicarb soda in 1 1/2 teaspoons boiling water. Beat half of flour mixture into butter mixture. Beat in bicarb soda mixture, then remaining half of flour mixture. Mix in chocolate. Turn onto a piece of glad wrap (plastic wrap). Pat dough into a disc about 3 cm (1 inch) thick. Seal with wrap and refrigerate until firm – approx 2 hours.
4. Heat oven to 160 deg C (325 deg F). Roll dough into small balls (or use a small/mini ice-cream scoop) and place on baking sheets 6 cm (2 inches) apart. refrigerate for 20 minutes. Roll balls in sugar. Bake until surfaces crack slightly, approximately 10-12 minutes. Transfer to a wire rack to cool.