Line an 8x8-inch tin with baking paper, leaving a little bit hanging out of each side so that it's easy to pull the tiffin out once set.

In a large bowl, break the Digestive biscuits into chunks using the end of a rolling pin or your hands. Don't crush them completely- it's best to have some larger pieces with a few crumbs for the best texture.

Add the vegan margarine, golden syrup and cocoa powder to a small saucepan. Place it over a low heat and stir occasionally until the margarine has melted.

Add the chocolate to the saucepan and continue to stir over low heat until it has melted. The mixture should be smooth and glossy.

Pour the mixture into the bowl with the Digestive biscuits then add the raisins. Mix well until everything is coated in chocolate.

Transfer the tiffin mix into the lined dish and use the bottom of a cup or clean hands to press it firmly into place.

Melt the chocolate for the topping and pour it into the dish. Use the back of a spoon to spread it evenly over the tiffin.

Refrigerate for 3 hours before cutting into 16 squares. I recommend running the knife under hot water before each slice to prevent the chocolate from cracking.