How to cook
In a bowl, mix the yoghurt with the baking soda. Add the sugar, oil and sifted flour.
Stir well and add the grated plain wafers. Stir again and pour the mixture into a tray with baking paper.
Bake at 392°F (200 °C) for about 35 min. Take the cake out and smear it with the butter. Sprinkle with grated chocolate wafers. Leave to cool and serve.