Into a bowl, sift in the flour, baking powder, baking soda and salt. Set aside.
In another bowl, add in soften butter and sugar. Whisk for a few minutes until fluffy. Add in the eggs, one by one, and mixing good after each addition.
Add in vanilla extract and buttermilk. Mix everything to combine. Finally add in sifted flour and ground hazelnuts. Mix everything together just to combine. Don't over mix to avoid hard texture cake.
Spoon the batter into a 10 inch (25 cm) bundt pan that has been buttered and floured beforehand. Spread the batter evenly. Bake in a preheated oven at 320ºF (160ºC) for 55 minutes or until golden brown and fully cooked. Cover the pan loosely with an aluminium paper if the cake browns too fast.
Remove from the oven and leave the cake to cool a bit, around 5 minutes. Then place a rack on top of the pan and carefully flip it. Mind the hot pan. Leave the cake to cool completely.
Heat the cream in a pot until just before it starts to simmer. Pour the cream into a bowl containing chocolate pieces. Leave untouched for 3-4 minutes for the cream to slowly melt the chocolate. After that, slowly whisk the mixture until smooth.
Immediately pour on top of the cake. Sprinkle some chopped hazelnuts on top and serve. Enjoy!