Chocolate and Vanilla Sponge Sandwiches
Preheat the oven to 190°C (170 fan) | 375°F | gas 5 and line two large baking trays with non-stick baking mats.
Combine the flour, baking powder, sugar, butter, eggs and vanilla extract in a bowl and whisk together for 2 minutes or until smooth. Separate it into 2 bowls and stir the cocoa powder into one of them.
Spoon the plain mixture down one side of a piping bag fitted with a large plain nozzle and spoon the chocolate mixture down the other side. Pipe 18 walnut-sized domes onto each tray.
Transfer the trays to the oven and bake for 10 - 15 minutes. The mixture should spread a little whilst cooking and the cakes will be ready when springy to the touch. Leave the cakes to cool on the tray then lift them off with a palette knife.
Sandwich the cakes together in pairs with chocolate spread.