Sour cream ganache
1.Preheat oven to 160°C. Grease a 21cm bundt pan well.
2.Beat cake ingredients in a medium bowl on low speed with an electric mixer until just combined. Increase speed to medium, beat until smooth and changed to a paler colour. Add sour cream, beat until just combined. Spread mixture into pan.
3.Bake cake 1 hour or until a skewer inserted into the centre comes out clean. Stand cake in pan 5 minutes before turning, top-side up on to a wire rack to cool.
4.Meanwhile, to make sour cream ganache, stir chocolate and sour cream in a medium heatproof bowl over a medium saucepan of simmering water (don’t let water touch base of bowl), stirring occasionally, until smooth and chocolate has melted. If ganache becomes too thick, add enough of the water to thin it down.
5.Drizzle ganache over cold cake.