Step 1

Preheat oven to 160°C. Line a 7cmdeep, 10.5 x 20.5cm (base measurement) loaf pan with non-stick baking paper.

Step 2

Place the dark chocolate, butter and water in a heatproof bowl over a saucepan half-filled with simmering water (make sure bowl doesn't touch the water). Use a metal spoon to stir until chocolate melts and mixture is smooth.

Step 3

Combine the sugar, combined flours and cocoa powder in a bowl. Add the chocolate mixture and egg and whisk until combined. Pour into the lined pan. Bake in oven for 1 hour 10 minutes or until crumbs cling to a skewer inserted into the centre. Set aside in the pan for 15 minutes to cool before transferring to a wire rack to cool completely.

Step 4

Meanwhile, to make the frosting, place the milk chocolate and cream in a heatproof bowl and place over a saucepan half-filled with simmering water (make sure the bowl doesn't touch the water). Use a metal spoon to stir until the chocolate melts and mixture is smooth. Set aside for 25 minutes to cool.

Step 5

Use a vegetable peeler to slice the white chocolate into thin pieces. Place cake on a serving platter. Pour frosting onto the centre and spread to the edges, allowing it to run over the sides. Sprinkle with white chocolate to serve.