This is the most amazing chocolate cake. There is no flour in it so it is not a spongey cake but instead is rich, gooey and fudgy… a bit like a giant chocolate truffle. It is surprisingly easy to make and will feed a lot of people.
Preheat your oven to 120C. Using the extra butter, grease a 25cm cake tin and line with parchment paper.
Break the chocolate into pieces and melt with the butter in a bowl over simmering water.
Beat the eggs with 70g of the sugar with an electric whisk until the volume quadruples.
Heat the remaining sugar with 100ml water until dissolved into a light syrup. Pour the hot syrup into the chocolate mixture and leave to cool slightly.
Add the cooled chocolate mixture to the eggs and fold together using a metal spoon or spatula. Pour into the tin.
Put a folded tea towel in the bottom of a baking tray. Put in the cake and pour in enough boiling water to come three quarters of the way up the tin.
Bake for 50 minutes until just set (it should still wobble slightly). Leave to cool in the water.
Once cooled, remove from the tin using the parchment paper to pull it out. Cutting is easier if you run your knife under hot water before each slice.