Add crushed cones, salt, and sugar to a food processor. Process until fine crumbs form. Slowly pour butter through the feed tube while the machine is running and process until the mixture resembles wet sand.
Press crumbs into the bottom and up the side of an 11-inch tart pan with removable bottom. Bake until crust is golden and set, about 15 minutes. Cool completely in pan on a wire rack.
In a small saucepan, bring ¾ cup cream to a simmer; remove from heat and add chocolate. Let stand 5 minutes then whisk to combine. Stir in Nutella. Cool the mixture to room temperature.
With an electric mixer, beat 1 cup cream with powdered sugar in a large bowl until stiff peaks form. Gently fold in chocolate and Nutella mixture until combined.
Pour filling into cooled crust and refrigerate until chilled and completely set, about 1 hour.
To serve, top tart with hazelnuts and whipped cream if desired.
Hazelnut topping (if using)
In a small saucepan, combine peeled hazelnuts, granulated sugar, salt, and ¼ cup water. Bring to a boil and cook for one minute.
Strain hazelnuts and spread in a single layer on a parchment-lined baking sheet. Bake until they are toasted and shiny, 12-15 minutes. Let cool completely.
Don’t overbake the crust. It will taste bitter and become too hard.
The Nutella is optional but I highly recommend it. It adds a delicate hint of hazelnut flavor without overpowering the filling.
Depending on where you live, finding skinned hazelnuts can be a challenge. See the tip in the post on how to peel them.
You can substitute hazelnuts with nuts of your preference or omit them if your household has nut allergies (in that case, omit Nutella as well – it’ll still taste delicious).
The mousse tart will keep fresh in the refrigerator for up to a week.
Please keep in mind that nutritional information is a rough estimate and can vary significantly based on products used.