1. Preheat oven to 180°C. Grease two cake tins.2. Mix the cocoa and boiling water together until all the lumps are dissolved. Allow the mixture to cool.3. Beat the egg yellow together. beat the sugar in bit by bit until the mixture is thick and light yellow.4. Add the cooled cocoa mixture, oil and vanilla essence to the egg mixture.5. Sift the flour, salt and baking powder together into the mixture. Mix well together so that all the ingredients combine.6. In a separate bowl, beat the egg white until firm peaks can be formed. Then fold into the cake mixture with a metal spoon.7. Pour the cake mixture into the prepared tins and bake for 25-30 minutes.8. Remove from the oven and allow to cool slightly before removing from tins.