For the chocolate exterior, fill the 2 bowls with water, then place 1 small spoon in each bowl. Transfer the bowls to the freezer and freeze them for 12 hours.
Once the water has frozen, remove the bowls from the freezer and dip them in lukewarm water in order to remove the ice from the bowl. Temper the dark chocolate, then dip the ice in the tempered chocolate. Let the chocolate set, then carefully peel it away from the ice. Transfer the chocolate bowls to the refrigerator and chill for 20 minutes.
Boil the milk in a saucepan, then add in the chopped white chocolate. Stir everything together well, then let the mixture cool down to room temperature. Divide the white chocolate mixture into 2 equal portions. For the white chocolate ganache, transfer ½ of the white chocolate mixture to the refrigerator and let it chill for at least 4 hours. For the hazelnut mousse, whip the heavy cream and combine the other ½ of the white chocolate mixture with the whipped cream and chopped hazelnuts, transfer it to the refrigerator, and chill for 30 minutes.
Temper the white chocolate and stir in some red food coloring. Use a long spatula to spread a thin coat of the tempered red chocolate over the surface of a granite cutting board or a similar surface. Let the red chocolate set a bit, then use the wide spatula to push the chocolate up, creating natural folds and making the red chocolate resemble a wrapper. Repeat this process a second time, then transfer the red chocolate wrapper to the refrigerator and chill for 20 minutes. Set the leftover red chocolate aside for later.
Fill the first chocolate bowl with the hazelnut mousse and spoon a large dollop of Nutella into the center. Use a lighter to heat the bottom of plate and place the second chocolate bowl on top of it so that the edges melt slightly. Place the second bowl on top of the one filled with hazelnut mousse in order to make a ball out of the chocolate bowls.
Heat the remaining red chocolate, then dip the tips of the red chocolate wrappers into it. Secure 1 wrapper onto each side of the chocolate ball. Heat up the white chocolate ganache and pour it over the top of the stuffed chocolate candy.
