For the Crust:

1. In the bowl of your food processor add the flour, hazelnut meal, sugar, salt and butter. Pulse 3-4 times until the butter is broken up until the size of a pea.
2. With the processor running, slowly dribble water from the top, 1 tablespoon at a time until the dough forms together into a ball.
3. Remove the dough from the food processor and press into an 8 inch pie tin. Press the dough into an even layer on the bottom, out to the sides and crimp the edges as desired.
4. Place into the refrigerator to chill for 25 minutes.

For the Chocolate Mousse:

1. While the pie dough is chilling, prepare the filling.
2. Add the egg whites and sugar in a bowl set over a double boiler and continuously whisk for about 2-3 minutes until the egg whites are foamy and the sugar has completely dissolved.
3. Transfer to a stand mixer fitted with a whisk attachment and whip on high for about 6-7 minutes until you’ve reached stiff peaks.
4. In another bowl set over a double boiler melt the chocolate, let cool slightly and then stir in 1/4 cup of the chocolate hazelnut spread.
5. Let the chocolate cool completely and fold in the whipped egg whites. Set aside.
6. In the same mixing bowl pour in 1 cup of heavy cream, vanilla extract and salt. Whip on high until you’ve reached medium to stiff peaks about 4-5 minutes. Keep an eye on the heavy cream to make sure you don’t overbeat the whipped cream.
7. Gently fold in half the whipped cream into the chocolate mix, then add the liqueur and then the remaining whipped cream. The mousse will be very loose at this point.
8. Place in the refrigerator to chill and remove the pie dough.

To Assemble the Pie:

1. Heat your oven to 350°F.
2. Place parchment paper on top of the pie dough and weigh down with pie weights.
3. Bake for 15 minutes, remove the parchment and pie weights and bake for another 10. The dough will not brown much but should be dry and not have a shiny look to it.
4. Let cool completely and then spread the remaining 1/4 cup of chocolate hazelnut spread on the bottom of the crust.
5. Remove the mousse from the fridge and pour on top.
6. Cover with plastic wrap and place in the fridge to chill completely for at least 6 hours or overnight.

To Serve:

1. When ready to serve, whip the remaining whipped cream in a stand mixer fitted with a paddle attachment until stiff peaks form and spread on top of the pie.
2. Top with the chopped hazelnuts.
3. Pie should be served chilled.
4. Pie will keep about 2-3 days in the refrigerator.