Chocolate Stripe Cake

For the cake: heat the oven to 180°C (160° fan) | 350°F | gas 4. Grease a 23 cm | 9" cake tin and a 15cm | 6" cake tin or angel food cake tin and line the bases with non-stick baking paper.

Beat the butter and 225 g | 1 cup sugar in a mixing bowl until pale and fluffy. Add the vanilla and beat until blended.

Add the egg yolks one at a time and beat well after each addition.

Add half the flour, followed by the milk in 2 additions, then mix in the remaining flour.

Divide the mixture into 2 equal portions, add cocoa powder to one portion and mix well. Set both aside.

Whisk the egg whites until soft peaks form, then gradually add the remaining sugar and whisk until stiff.

Divide the egg whites into 2 portions. Add 1 portion to the plain mixture and 1 portion to the cocoa mixture. Gradually fold in until incorporated.

Using a tablespoon, scoop 1 tablespoon of plain mixture into the centre of each tin. Scoop 1 tablespoon of cocoa mixture on top of the centre of the plain mixtures.. Alternate the 2 mixtures until all the mixtures are used. Don't stop and wait until the previous mixture spreads and don't spread the mixture or tilt the pan. It will spread by itself and fill the tin gradually.

Bake the larger cake for 40-45 minutes and the smaller cake for about 30 minutes (depending on the depth of the tin) until a skewer inserted into the centre comes out clean. Reduce the oven temperature if the top browns too quickly or start to crack. Remove from the oven. Immediately run a small thin knife around the inside of the tins to loosen the cakes, then invert the cakes onto a wire rack. Turn the cakes back over and cool completely.

For the frosting: combine all the ingredients in a large heatproof bowl set over a pan of simmering (not boiling) water.

Whisk with an electric whisk at high speed for 7-10 minutes, until the frosting is thick and fluffy. Remove from the heat and continue to whisk until slightly cooled.

Invert the larger cake onto a serving plate and spread with a thin layer of frosting. Place the smaller cake on top.