Step #1 Note: to toast & skin hazelnuts: place nuts on a baking sheet & bake in a 350° oven for about 10 mins or until they are fragrant.
Step #2 Remove the pan from the oven; wrap the nuts in a clean kitchen towel, & allow nuts to cool for 10-15 mins.
Step #3 Rub the nuts with the towel to remove the skin (ok if bits of skin stick to some of the nuts).
Step #4 To make the pie: place the skinned nuts in the container or a food processor/blender; chop the nuts very fine.
Step #5 In a large mixing bowl, mix the cream & vanilla; using an electric mixer, whip the cream until stiff peaks form.
Step #6 Put the Nutella in another mixing bowl; stir in the 1/4 of the whipped cream; carefully fold the lightened Nutella mixture back into the remaining whipped cream.
Step #7 Fold in sliced hazelnuts.
Step #8 Scrape the filling into the prepared pie shell; smooth over with a rubber spatula.
Step #9 Cover up pie with plastic wrap & put in the fridge at least 6 hrs or up to 1 day (until filling is completely set).
Step #10 May top this with whipped cream, if desired.