To begin, melt the butter with the sugar and the golden syrup in a pan on a medium heat until all is dissolved together.
Next, add in the Cocoa. You can use Drinking Chocolate, but I prefer the rich flavour that Cocoa gives. Also add the raisins. You can add as many as you like, it depends how raisiny you like things. I added enough to cover two thirds of the bottom of the pan. Let Simmer for a few minutes.
Whilst that's simmering, break up the biscuits. You can break them up with your fingers or use the age old method of bashing them with a rolling pin. Make sure the biscuit chunks aren't too big else everything will fall apart later.
Mix biscuits in with Raisins and Syrup, then add the rest of your goodies. I have added Maletesers and rolled oats as I like the crunch from the Maltesers and the slight chew from the oats, but it doesn't matter. Make sure you don't overfill the Tiffin. You want everything to be evenly coated.
Line a baking tray with cling film, and press Tiffin into it to set. You don't need to press the Tiffin into all corners. As you can see from my picture I'm only using a third of the tray, and that's fine because the Tiffin will hold together. Put it to set in the fridge for an hour.
When the hour is coming to a close, start melting your Chocolate. I did that in a microwave. Once it's all melted, spread the chocolate ontop of the tiffin. The surface probably won't be even, but it doesn't matter. Pop back in the fridge for a few hours.
When you're satisfied with how much it has set, cut Tiffin into manageable squares, serve and devour. Yum!