Line a baking tray with baking paper. Stir sugar and syrup in a small deep saucepan over medium heat for 8 minutes or until sugar dissolves and mixture boils. Reduce heat to low and simmer for 8 minutes or until mixture turns a golden caramel colour. Stir in bicarbonate of soda (be careful, mixture will bubble up quickly). Pour immediately over tray and set aside. When cold, break into pieces.
Grease a 20x12cm loaf pan and line with baking paper, with sides overhanging. Stir chocolate and margarine in a heatproof bowl over a saucepan of simmering water for 5 minutes or until melted. Cool for 10 minutes. Stir in hazelnut, dried fruit and toffee. Pour into pan, smooth top and chill for 2 hours to set. Remove from pan, slice and serve.