1

Preheat oven to 180°C. Line the base and side of a round 22cm springform cake tin with baking paper.

2

Place the chocolate and cocoa powder in a large bowl.

3

Combine the brown sugar, flour and salt in a saucepan. Whisk in ⅓ cup of milk until smooth. Whisk in the remaining milk. Cook over medium-high heat, stirring constantly until mixture boils. Reduce heat to medium and cook, stirring constantly, for 1 minute. Spoon over the chocolate mixture and set aside for 1 minute. Whisk until smooth. Whisk in the egg yolks until combined.

4

Use an electric mixer to beat the egg whites until foamy. Add the cream of tartar and beat until soft peaks form. Add the caster sugar and beat until thick and glossy. Whisk one-third of the egg white mixture into the chocolate mixture. Gently fold the remaining egg white mixture through the chocolate mixture in 2 batches. Spoon the mixture into the prepared tin and smooth the surface.

5

Place the cake in a large baking pan. Pour in enough boiling water to come halfway up the side of the cake tin. Bake for 25 minutes or until a crust has formed and the cake is almost set (the centre may still move slightly). Remove the cake tin from the pan and cool on a wire rack. Place in the fridge overnight to set.

6

Remove the cake tin and discard the paper around the side. Carefully invert the cake onto a board lined with baking paper. Place a serving plate upside down over the cake and flip to turn the cake onto the serving plate. Place in the fridge until ready to serve. Dust with extra cocoa to serve.