Preheat oven to 160ºC (325ºF). Place the butter, chocolate, vanilla and water in a saucepan over low heat and stir until melted and smooth. Allow to cool to room temperature.Place the eggs and sugar in the bowl of an electric mixer and beat for 6 minutes or until pale and thick. Add the chocolate mixture and beat until combined. Fold through the flour and cocoa and pour into a lightly greased 22cm springform cake tin lined with non-stick baking paper. Bake for 1 hour 30 minutes or until cooked when tested with a skewer. Allow to cool in the tin. Remove the cooled cake from the tin and follow instructions, below, to make a shell. Set aside.
To make the lemon curd, place 1 cup (250ml) milk and the sugar in a saucepan over medium heat and stir until the sugar is dissolved. Place the cornflour and remaining milk in a small bowl and stir to combine. Pour into the milk and sugar mixture and stir to combine. Increase heat to high, add the butter and whisk until melted and combined. Add the lemon juice, lemon rind and egg yolks, reduce heat to medium and cook, whisking continuously, for 6–7 minutes or until thickened. Pour the lemon mixture into the cake shell and refrigerate for 2 hours or until set.
To make the meringue icing, place the sugar, water and cream of tartar in a saucepan over high heat and stir until the sugar is dissolved. Bring to the boil, reduce heat to low and cook for 3 minutes. Place the eggwhites in the bowl of an electric mixer and whisk until soft peaks form. While the motor is running, gradually add the sugar mixture and beat until thick and glossy. Spoon the meringue over the cake to serve. Serves 8–10.
+ To make the cake shell, step 1: Turn the cooled cake out onto a plate and place an18cm-round plate, up-side down, in the centre of the cake. Using a small, sharp knife, make a shallow cut around the plate.Step 2: Remove the plate and use a dessert spoon to carefully scoop out ¾ of the cake.Step 3: Carefully spoon the lemon curd into the cake shell and use a palette knife to smooth the top.
Tip: Take care not to scoop out too much cake or it will leave the base weak, making it difficult to remove slices from the cake. It’s a good idea to ensure the base is at least 1cm-thick.