Preheat oven to 350 degrees. Line cupcake tins with cupcake papers.
Melt the chocolate over a double boiler or in a microwave. Set aside and allow to cool slightly.
In a small bowl, mix the flour and baking soda.
In another small bowl, mix the buttermilk and vanilla, and set both bowls aside.
In the bowl of a stand mixer beat the butter, sugar and brown sugar together until fluffy.
Add the chocolate and the eggs, one at a time waiting until each is fully mixed in before adding the other.
Alternate adding the flour mixture and buttermilk mixture until everything is combined. Do not over mix.
Using an ice cream scoop divide batter into tins and bake for 20-25 minutes. Cool completely before filling and icing.
For the chocolate ganache place the chocolate chips in a small bowl and set aside. Heat the the heavy cream in a small sauce pan and almost bring to a boil. Pour the heavy cream over the chocolate and let it sit for about 3 minutes.
Whisk the mixture together until fully combined and glossy. Once completely cooled the ganache will thicken. Place into a disposable pastry bag or a plastic zipper bag with the corner cut off
Using a sharp knife or an apple corer remove the center of the cupcake. Fill each of the cupcakes and cover with the removed piece of cupcake.
For Nutella Mousse Recipe: HERE
Frost each cupcake with the Nutella Mousse using a star tip with a pastry bag or frost by hand and decorate with Ferrero Rocher chocolates.