First, blend the biscuits in a processor then place in a mixing bowl.
Melt the butter, sugar, syrup/honey and cocoa powder in a saucepan on medium heat but be careful not to burn.
When melted and slightly frothy add the mixture to the crushed biscuits, add the raisins and mix well until combined.
Pour the biscuit mixture into a suitable-sized square tin that's similar to what you would use to bake a Swiss roll cake.
The mixture should resemble a thick, chocolaty, doughy paste. Press your paste down flat into the tin so that it's roughly at least 2 cm thick.
Then set aside and begin to melt the cooking chocolate to pour over the mixture in the tin. I find it best to break the chocolate up into cubes and place it in a glass mixing bowl that will sit over some boiling water in a saucepan while stirring. (I don't like the taste or smell the microwave leaves on the chocolate)
Then you can grate the white chocolate or chop up some nuts and sprinkle on top for garnish. (I use a potato peeler for this instead of a grater for larger flaky swirls)
Pop your baking tin into the fridge and leave for about 1 hour to set.
To serve, you can cut into about 20 square pieces if you want more generous portions or you can half these squares into rectangles for even more pieces if you want them smaller.
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