1.Preheat oven to 180°C. Grease and line oven trays with baking paper.
2.In a medium bowl, whisk sugar and eggs until combined; stir in sifted flours, nuts, sultanas and cherries. Shape dough into two 30cm logs. Place on trays; flatten slightly. Bake about 30 minutes. Cool on trays.
3.Reduce oven temperature to 140°C.
4.Using a serrated knife, slice logs diagonally into 5mm slices. Place slices, in a single layer, on baking-paper-lined oven trays. Bake about 15 minutes, turning halfway through baking, or until dry and crisp. Cool on wire racks.
5.Break dark chocolate into a medium heatproof bowl. Place over a medium saucepan of simmering water (don’t let water touch base of bowl); stir until chocolate is melted. Transfer chocolate to a small cup. Dip one end of biscotti into chocolate; drain excess chocolate. Place on baking-paper-lined trays. Stand at room temperature until chocolate sets.