Preparing the Hazelnut Shortbread Base

1. Preheat your oven to 350°F (175°C) and line a springform pan with parchment paper.
2. In a food processor, pulse the toasted hazelnuts with sugar until finely ground.
3. Add flour, softened butter, cocoa powder, and salt. Pulse until a smooth dough forms.
4. Press the dough evenly into the prepared pan.
5. Bake for 18-20 minutes until set. Let cool completely.

Creating the Luxurious Hazelnut Chocolate Mousse

1. Sprinkle gelatin over cold water and let it bloom for a few minutes.
2. Gently warm the gelatin mixture until dissolved.
3. Mix the gelatin with chocolate hazelnut spread.
4. Whisk in mascarpone cheese until smooth.
5. Whip the heavy cream to soft peaks and gently fold into the chocolate mixture.
6. Spoon the mousse over the cooled shortbread base.
7. Refrigerate for at least 3 hours to set.

Finishing with a Stunning Chocolate Glaze

1. Heat heavy cream in a saucepan.
2. Remove from heat and whisk in chopped bittersweet chocolate.
3. Stir until smooth and glossy.
4. Pour the glaze over the chilled mousse cake.
5. Allow the glaze to set before serving.