True to its name this cake never fails and kids particularly love it. You could swap the chocolate with vanilla and lemon zest or an aromatic mix of nutmeg, ginger and cinnamon then a coffee-buttercream dressing.
Preheat oven to 180C and grease and line a loose-bottomed 20cm circular or rectangular cake tin.
Place all ingredients in the bowl of your Thermomix with butterfly attachment and mix 5 mins/speed 5.
Pour into the prepared cake tin and smooth over the top.
Bake for 35-40 minutes. Let cool in the tin for 5 minutes before turning out to a rack to cool completely.
For the icing, combine all ingredients and stir well until smooth, add boiling water as needed so you have a lovely thick, spreadable icing.
Once cake is completely cool, trim edges then spread with icing and top with sprinkles or silver cachous.