Preheat oven to 350 F. Line a cupcake tin with liners.

In a large bowl, whisk to combine the flour, cocoa, baking soda, and salt. Set aside.

In the bowl of an electric mixer fitted with a paddle attachment, cream the butter and sugar on medium high for 2 minutes until creamy. Scrape down the sides of the bowl and add the eggs followed by the vanilla. With the mixer on low, alternatively add the milk and dry ingredients until just combined. 

Pour the batter into the cupcake tin. Fill each cup about 2/3 full.

Bake 17-20 minutes or until a toothpick comes out clean. Allow to cool 10 minutes in the cupcake tin then transfer to a wire rack to cool. Cool completely before stuffing and frosting.

Once cooled, scoop out a chunk of the cupcake from the center.

Fill each cupcake with about 1 teaspoon of Nutella then place the top chunk of the cupcake back on top. Don't worry about how it looks since you're going to cover it with frosting. 

In the bowl of an electric mixer with the paddle attachment, beat the butter on medium high speed for one minute. Add the Nutella and beat the Nutella and butter for a minute.

With the mixer on low speed, add the powdered sugar, vanilla, heavy cream or milk and a pinch of salt. Increase the speed to medium high and beat for two more minutes or until creamy, light and fluffy.

Place some chocolate chips in a bowl and microwave them in twenty second intervals. Stir in between intervals and continue until just melted. Dip each hazelnut halfway in the chocolate then place on wax paper to dry. Place one on top of each cupcake. 

Chop desired amount of hazelnuts. Sprinkle on top of frosted cupcakes.