• Cooking oil spray, for greasing
• 150g dark chocolate, chopped
• ¾ cups hot water
• 200g unsalted butter, chopped
• 1½ cups caster sugar
• 3 eggs
• 1 cup self-raising flour, sifted
• 1 cup plain flour, sifted
• ¼ cup cocoa powder, sifted
Chocolate buttercream icing
• 300g unsalted butter, chopped
• 300g dark chocolate, chopped
Note: Allow 15 minutes cooling time
Preheat oven to 160°C. Spray a 20cm round cake tin with cooking oil and line base and side with baking paper.
Put chocolate, water and ½ the butter in a medium saucepan over a low heat. Cook, stirring with a spatula, until mixture is melted and smooth, but not boiling.
Transfer mixture to a large bowl and set aside to cool for 15 minutes or until mixture is at room temperature.
Meanwhile, put sugar and remaining butter in the bowl of an electric mixer and beat for 5 minutes or until light and fluffy. Add eggs, 1 at a time, beating well after each addition. Add chocolate mixture and beat to combine. Fold in flours and cocoa powder until combined.
Spoon batter into prepared tin. Bake for 1¼ hours or until cooked when tested with a skewer. Cool in tin for 5 minutes, then turn out, upside down, onto a wire rack to cool completely.
Meanwhile, to make icing, put butter and chocolate in a glass or ceramic bowl over a saucepan of simmering water. Stir until melted and smooth. Set aside to cool for 30 minutes or until mixture is at room temperature. Beat, using a whisk or electric mixer, for 2 minutes or until mixture is thick and spreadable.
Turn cake right-side up. Cut cake in half horizontally. Put base on a cake stand or serving platter. Spoon 1 cup of the icing on centre and spread to edges, using a palette knife. Sandwich with remaining cake half.
Spoon remaining icing on cake and spread to coat top and side. Serve.