Preheat the oven to 350˚F. Lightly grease and flour a 10-inch bundt pan and set aside.
In a medium bowl, combine the flour, baking powder and salt and set aside. In a standing mixer fitted with a paddle attachment, or with an electric hand mixer, cream together the butter and sugar until light and fluffy, about 3 – 5 minutes. With the mixer on low, add the beaten eggs in a slow stream and beat until well combined. Gradually add the flour mixture, followed by the milk, and beat until just combined, and a smooth batter forms.
Pour the batter into the prepared bundt pan. Evenly space the Ferrero Rocher balls in a circle over the top and gently push them into the batter. Use a spatula to spread the batter evenly over the top so that the balls are no longer visible. Transfer to the preheated oven and bake, turning the pan once halfway through, for 1 hour, or until a toothpick inserted into the center of the cake comes out clean.
Transfer the cake to a wire rack and allow to cool for 5 – 10 minutes in the pan. Invert the cake onto the wire rack to remove it from the pan and allow to cool completely.
For the drizzle, in a medium bowl, melt the chocolate and butter in 30 second intervals in the microwave, stirring in between, until smooth. Add the corn syrup and stir to combine. Pour the chocolate over top of the cooled cake, allowing it to run down the sides. Sprinkle the toasted hazelnuts over the top. Enjoy!