Place the base mix, butter, egg and 125 ml water in a mixing bowl and work into a smooth dough with the whisks of the hand mixer. Pour the dough onto a greased baking tray (32x37 cm), smooth it down and bake in a preheated oven (electric cooker: 200 °C/ gas: level 3) for 10-12 minutes. In the meantime sieve icing sugar. Mix icing sugar and 3-4 tablespoons of water with the whisk of the hand mixer. Take the cake out of the oven, while still warm, spread the icing sugar on top. Let the cake cool down a bit and then cut it into 15 pieces (approx. 7x11 cm). Decorate as you like with paper wafers