Prepare baking pans by spraying them liberally with baking spray. Set aside

Place 1 cup of hazelnuts in a food processor and pulse until the nuts are finely ground. Set aside.

In a large bowl, whisk together the flour, 1 cup of confectioner's sugar, cocoa powder, salt, and ground hazelnuts.

Switch to a wooden spoon or spatula and stir the melted butter, water, and vanilla into the flour and hazelnut mixture. Set aside.

In the bowl of a stand mixer (or a large bowl with a hand mixer), whip the egg whites on high until soft peaks form.

Spoon half of the whipped egg whites into the flour and hazelnut mixture and gently fold to incorporate and lighten the batter. Add the remaining whipped egg whites to the batter and gently fold to incorporate.

Divide the batter evenly into 3 prepared cake pans.

Bake cakes in preheated oven for 18-20 minutes. Remove the pans from the oven and cool on a cooking rack for approximately 10 minutes.

Place a second baking rack on top of the partially cooled cakes and carefully flip the pans and racks together. Remove the cake pans from the cakes. Place the cooling rack on top of the cakes and carefully flip the cakes again so the cakes are right-side-up. Cool the cakes completely.

Whip the heavy cream in the chilled bowl of a stand mixer, or a large bowl with a hand mixer, until soft and fluffy.

Add 3 tablespoons of confectioners sugar and 3 teaspoons of vanilla to the whipped cream and stir to combine.

Spread 2 tablespoons of the chocolate hazelnut spread evenly on top of each cooled cake round.

Place one of the cake rounds on a serving plate, chocolate hazelnut spread side up.

Top the cake with approximately 1½ cups of whipped cream and spread the whipped evenly over the cake.

Continue layering the cakes and whipped cream, ending with a layer of whipped cream to end.

Rough chop the remaining 1 cup of hazelnuts and sprinkle on top of the cake to finish.

Refrigerate until ready to serve.