Put the biscuits in a blender and blend coarsely. If you don't have one, use a plastic bag and a meat mallet to crush them. Put them in a bowl.
Chop the apricots and dates into small pieces. Soak the raisins in the rum. Put the butter in a casserole, heat it on the stove to melt, add the golden syrup and cocoa. Stir and crumble in the chocolate.
Place baking paper in a round or square baking dish and pour in the mixture. Even it out, smooth it and put in the fridge to harden for 1 hour.
Make the chocolate layer by heating the confectionery cream in a casserole on the stove, take it off right before it comes to a boil. Crumble the milk chocolate into it and leave it to soften for 1 min., then stir until you get a smooth chocolate ganache.
Take the baking dish with the Tiffin out of the fridge and pour the chocolate ganache over it, even it out and put it back in the fridge for at least 6 hours to harden. When serving, take it out of the fridge, carefully unstick the baking paper along the sides and cut it into squares.
Notes: An exceptionally sweet English dessert that's widely popular in the U.S. The original recipe calls for covering it with pure melted chocolate but there are many improvisations which improve on this wonderful dessert.
If you can resist, leave it to cool and harden well. Use a baking dish with a smaller diameter to get a taller confectionery. It's quite similar to sweet salami, which I make often. Highly caloric but extremely sweet!