Pre-heat the oven to 175ºC.

Grease and flour a loaf tin (dimensions 21.6 cm wide, 11.4 cm deep, 5.5 cm height).

Whisk eggs, sugar and vanilla sugar until pale and foamy.

Blend flour and baking powder together and fold into mixture alternately with melted butter.

Then fold in the mashed banana.

Put in a loaf tin and cook in the centre of the oven for about 50 minutes or until the cake springs back when prodded.

Leave to cool for a few minutes and then turn out onto a wire rack to fully cool.

Make the chocolate topping by melting the chocolate and butter in a small glass bowl over a pan of barely simmering water, stirring until melted.

Scrape the chocolate out of the bowl and onto the cake with a spatula.

Use a palette knife to spread the chocolate evenly over cake.

Allow to set (we have never managed to wait this long though)!