Heat oven to 180 C (fan 160 C). Grease 2 x 8" round sandwich tins and line bases with baking paper.

Mix cocoa and boiling water in a large bowl, and form a paste.

Add the butter, eggs, milk, flour, baking powder, castor sugar and most of the finely grated zest of an orange. Beat until combined but be careful not to overmix.

Divide mixture between prepared tins. Bake for 20-25 minutes until sponges are well risen and shrinking away from the sides of the tin. Turn out of tins onto cooling rack and leave to cool completely.

ICING: Break the Bournville chocolate into small pieces into a bowl . Add the cream. Stand bowl over pan of simmering water for 10 minutes until melted. Ensure bowl doesn't touch the water. Stir occasionally. Set aside to cool until thickens to spreadable consistency.

Spread tops of both sponges with apricot jam. Spread the top of one with half the icing and put the other on top. Cover top of cake with rest of icing. Make large S shapes with small palette knife to give a swirl effect. Scatter the top liberally with the crushed Flake. Garnish with rest of zest.