Preheat your oven to 350 degrees. Spray a bundt cake pan with non stick spray and sprinkle with cocoa powder.

Combine butter, cocoa powder, salt and water in a small saucepan over medium heat.

Cook until everything is just melted and remove from heat. Set aside.

Combine flour, sugars and baking soda in a large mixing bowl.

Add in half of cocoa powder mixture at a time, stirring until completely blended.

Add in the eggs, and stir until just combined.

Mix in the sour cream and vanilla and stir until completely smooth.

Pour into the prepared pan and bake for 40-50 minutes until an inserted toothpick comes out clean.

Let the cake cool in the pan for 15 minutes then invert onto a cooling rack to cool completely.

Heat the heavy cream and sugar in a small sauce pan over medium heat until the sugar is dissolved.

Put chocolate and corn syrup in a medium sized bowl and pour heavy cream over the top.

Allow to set for 2 minutes, before whisking until smooth.

Allow to cool until a little bit thickened, about 15 minutes. Then drizzle over the top of the cake to cover.