- Preheat the oven to 200 C / 180 C fan / Gas 6. Grease a 900g loaf tin and line with baking parchment.
- Cream together one of the eggs and all of the sugar. Add in the margarine and the other egg. Mix for a while until thick and creamy. Slowly add in flour and beat until smooth.
- Separate the mixture into two bowls. Add some cocoa powder to one bowl, and even a splash of black food colouring with it and beat until well mixed. To the second bowl add the vanilla extract and stir.
- Take a spoonful of vanilla cake mixture and blob it in the centre of your tin. On top of the vanilla mixture add some chocolate mixture; continue filling up the tin, alternating between flavours.
- Bake in the preheated oven for 30 to 40 minutes, or until risen and a skewer inserted into the centre comes out clean, resist the urge to open the oven door during cooking as this can cause the cake to collapse. Remove from the oven and allow to cool completely upside down before decorating (see tip), slicing and serving.
If preferred you can decorate with some fondant to look like zebra stripes. Roll out black fondant and cut random thin strips to look like zebra stripes, set aside. Roll out white fondant large enough to cover the cake. Cover cake with apricot jam then lay the white fondant on top to cover completely. Carefully lay some strips of the black fondant on top using apricot jam to stick them down. If you do not want to use fondant, this cake is also delicious covered in gooey dark chocolate.
This cake is easily browned, so if needed, cover with tin foil 'hat' during final 5 to 10 minutes in oven.