Preheat the oven to 180°C/350°F/Gas Mark 4. Lightly grease two 7 inch cake tins. If using 2 cake tins, you will leave half the mixture until the first two cakes have baked. If using 4 cake tins, prepare them all now. In a jug, add the boiling water and cocoa powder, mix until smooth, then leave to cool.
600 ml boiling water, 150 g cocoa powder
In a large bowl, sieve the flour and add the baking powder, baking soda and salt. Leave this until needed.
360 g self-raising flour, 2 tsp baking powder, ½ tsp bicarbonate of soda, ½ tsp salt
In a stand mixer, cream together the butter and sugar until light and fluffy.
360 g butter or spread, 600 g caster sugar (superfine sugar)
Add the vanilla extract and then the eggs one by one. Beat well after you add each egg.
2 tsp vanilla extract, 6 eggs
Add all of the flour, and mix gently until combined. Fold in the cooled cocoa powder and water mixture.
Divide the mixture into the prepared cake tins. If you are using two cake tins and will bake in two sessions, put half the mixture aside.
Bake for 35 minutes, or until a cake tester (or knife or skewer) comes out clean from the centre of the cake.
Leave to cool in the tins until cool enough to touch then turn the cakes out onto a cooling rack.Now, if you used two tins, wash and regrease them and bake again with the rest of the mixture.