On low heat place the coating chocolate (broken into pieces) in a medium bowl over a pot of water (make sure bowl does not touch the water). Melt until smooth, stirring often with a spatula or whisk. Remove from heat and coat a silicone loaf pan 8.5 x 4.5 inch (22 x 11 cm), or a parchment paper lined loaf pan. Swirling or brushing the chocolate to coat evenly, drain any extra chocolate back into the bowl. Freeze the loaf pan for about 10-15 minutes or until hardens, coat one more time and freeze again for 10 minutes. The remaining chocolate will be used for the topping.
FILLING
While the coating is in the freezer, melt together the milk, white and dark chocolate the same way as above. Once it is melted, remove from the heat and stir in the Nutella, continue stirring until smooth. Fold in the hazelnuts, remove the loaf pan from the freezer and add the hazelnut filling. Refrigerate for approximately 30 minutes. Remove from the fridge and cover with the remaining dark chocolate coating. Cover lightly with foil and refrigerate 3-6 hours. Remove from loaf pan and slice or chop into pieces.
Notes
If the Torrone becomes quite hard after being in the fridge, it might be best to let it sit for approximately 15 minutes before slicing, although I chopped it in large pieces instead.If you buy untoasted hazelnuts, then you can either place the hazelnuts in a large frying pan and heat on medium heat for approximately 2 minutes stirring occasionally, then remove from pan and let cool. Or bake in a pre-heated 350°F oven for 5 - 7 minutes, just be sure to remove them from the pan to a bowl so they don't continue to bake.
How to store Chocolate Torrone
It should be stored in an airtight container or plastic bag in the fridge. Or at room temperature as long as it is a cool and dry area. It will last up seven days.It can also be frozen in a freezer safe bag or container. It will keep for up to 6 months in the freezer.