Preheat the oven 175°C.
Melt the chocolate and butter in a glass bowl over simmering water. Remove from heat and let it cool.
Mix the flour, bicarb and sugar. Add the milk and egg, then combine well.
Fold in the melted chocolate and mix gently.
Pour the chocolate mixture into the bundt cake moulds. Put them on a tray.
Put the tray in the middle of the oven and bake for 20 minutes.
Test the cakes with a skewer - insert it in the cakes, if it comes out clean, they are done. It the skewer is wet, cook them for another 5 minutes and test again.
Remove the tray from the oven and let the cakes cool for 5 minutes in the mould, then turn them out onto a cooling rack.
When the cakes are completely cool frost them with cream, icing, melted chocolate - or just dust them with icing sugar and serve.