Preheat the oven to 180°C and grease two 20cm sandwich tins with baking parchment.
Mix cocoa powder and boiling water in a large bowl to make a paste.
Add the remaining cake ingredients and beat until combined.
Divide the mixture between the tins and bake for 25-30 minutes.
Melt the chocolate and cream together over a pan of simmering water for 10 minutes.
Allow the icing to cool until it is almost set.
Cool the cakes completely then spread the tops with apricot jam.
Sandwich the cakes with half the icing and spread the rest on top.
Create a swirl effect with a palette knife and dust with icing sugar.