Add the hazelnuts to a small food processor and blend until the hazelnuts are fine crumbs.
In a small mixing bowl, melt the butter. Add in the blended hazelnuts, flour, brown sugar, and salt and mix just until a cohesive dough forms.
Press the dough into the bottom and up the sides of an 8" tart pan.
Poke holes in the crust with a fork, then place it in the freezer for 10 minutes. After freezing, bake the crust for 10-15 minutes, until the edges start to turn golden brown.
Allow the crust to come to room temperature before filling and assembling.
Whipped Cream
Add the heavy whipping cream, sugar, vanilla, and salt to a medium sized mixing bowl. With a hand mixer (or a stand mixer fitted with the whisk attachment), beat the mixture until soft peaks form.
Set the whipped cream aside in the fridge until you're ready to assemble the pie.
Filling & Assembly
Add the dulce de leche and salt to a small mixing bowl. Mix (or beat with a hand mixer) until well combined.
Spread the dulce de leche carefully over the cooled crust, then slice a large banana and place the slices on top of the dulce de leche.
Pile the whipped cream high on to the pie, making sure to cover the bananas so that they don't brown. Garnish with sliced bananas & hazelnuts, then slice, serve, and enjoy!