Pre-heat the oven to 160C.
Beat the butter and sugar until pale, light and fluffy.
Beat in each egg, one at a time, until fully combined.
Stir in the flour and bicarbonate of soda until fully combined, then add the yoghurt, vanilla and sprinkles and mix until totally combined.
Grease your bundt tin very thoroughly and then cover the inside with a dusting of flour, tapping out the excess.
Fill the bundt tin with your batter, evenly spreading it.
Bake for 50 - 60 minutes.
Meanwhile, make the ganache. Chop the chocolate very finely and heat the cream in a small saucepan until almost bubbling.
remove from the heat and add the white chocolate. Stir until the chocolate is melted and you have a thick ganache. Put to one side (at room temperature).
The cake is ready when a skewer comes out clean. (Depending on the shape of the bundt tin you are using, it could need a little more or a little less time. It's worth checking at 45 minutes and if it's not cooked at 60, obviously leave it in until it is.)
Allow to cool in the tin for 15 minutes and then tap firmly on the worksurface and turn out.
When the cake is totally cold, top with the ganache and extra sprinkles.