Preheat the oven to 350°F. Melt the butter in a small saucepan on medium-low heat until it turns a golden-brown color and has a nutty smell, about 5-7 minutes. It will foam up during this time so keep stirring and checking the color under the foam. Once it starts to turn color, don't walk away as it can burn quickly. Let the butter cool while you make the rest of the crust.

Place the hazelnuts in a small pan over medium heat, stirring often, for about 5 minutes until lightly toasted. They will start to smell more fragrant. Place the graham crackers, toasted hazelnuts and salt in a food processor and pulse until finely ground. Add the slightly cooled brown butter and pulse a few times until combined.

Pour the crust mixture into a 9-inch removable bottom tart pan, pressing the crust into the sides and bottom of the pan. Use the bottom of a cup to firmly press down the crust mixture. Bake the crust for about 8-10 minutes until lightly golden brown and fragrant. Allow the crust to cool while making the filling.

In a medium bowl, add the chopped chocolate, Nutella, vanilla extract and salt. In a small saucepan, heat the heavy cream over medium low heat until bubbles begin to form at the edges of the cream. Do not boil the cream.

Once heated properly, pour the cream over the Nutella/chocolate mixture and place a plate or plastic wrap over the top of the bowl for about 5 minutes to allow the chocolate to melt. Stir the Nutella mixture well until it forms a smooth and shiny ganache.

Place the heavy cream and Nutella in the bowl of a stand mixer fit with the whisk attachment. Beat the cream and Nutella until it reaches at least soft peaks.

In a small pan over medium heat, combine the chopped hazelnuts, sugar, salt and water. Stir to combine the ingredients and coat the hazelnuts completely. Allow the sugar to dissolve and begin to turn golden brown while stirring frequently, for 3-5 minutes.

Pour the hazelnuts onto a piece of parchment or wax paper to allow them to cool. Before topping the whipped cream with the hazelnuts, break apart any larger pieces using your hands and then sprinkle on top of the Nutella whipped cream.