Grease inside a 23cm square baking tin and line the tin with baking paper.
In a heatproof bowl, put the chocolate, butter and golden syrup.
As the chocolate and butter melts and with the mixture becoming smooth, take off the heat and let it cool for 10 minutes.
Add salt and ground cinnamon and mix well.
Crush the biscuits in a freezer bag, using a rolling pin.
Mix the crushed biscuits into the melted chocolate mixture.
Add the mangoes and raisins and stir well. Make sure everything is coated well.
Mix in the marshmallows and combine well.
Pour the mixture into the prepared tin. Using the back of the spoon, flatten and press to the corners.
Put the tin the fridge for at least 1 hour or until it has set.
Take out of the fridge. Dust with icing sugar and slice into bars (size of the bars are entirely dependent on you).