Ingredients

Step by step

1. Preheat the oven to 180°C, fan 160°C, gas 4. Grease a 900g loaf tin with butter and line with baking paper. Place 70g of the chopped chocolate in a heatproof bowl and set over a pan of barely simmering water, until melted. Set aside to cool.
2. Place 100g of the butter, the sugar and tahini in the bowl of a stand mixer (or use an electric hand whisk). Beat until smooth and well combined. Beat the eggs and buttermilk in a jug, then beat into the batter. Fold in the flour and baking powder until well combined. Spoon half the mixture into a separate bowl. Fold 50g of the halva into one bowl and stir the melted chocolate and cocoa into the other.
3. Dollop alternate spoonfuls of each mixture into the prepared tin, then run a table knife through the mixture a couple of times to swirl it together. Transfer to the oven and bake for 50 minutes or until a skewer comes out clean. Transfer to a cooling rack, still in the tin, and leave to cool completely. (You can wrap the loaf cake in baking paper and freeze at this stage. Defrost, then finish the recipe.)
4. To make the glaze, add the remaining 30g butter and 50g chocolate to a large heatproof bowl and heat in the microwave in 30 second bursts until melted, stirring together. Stir in the icing sugar along with the golden syrup and 20ml just-boiled water. It should be runny but not too thin – add a little more icing sugar or hot water, if necessary.
5. Remove the cake from the tin and place on a wire rack set over a sheet of baking paper. Pour the glaze evenly over the cake until the top is covered and drips down the side, then decorate the cake with the remaining halva. Once the glaze has set, transfer to a serving board or plate and slice to serve. Store in an airtight container for 3-4 days.