Preheat the oven to 350 F Degrees.
Place hazelnuts onto a small baking sheet and roast them for 8-10 minutes. Set aside and allow to cool.
Increase the temperature of the oven to 375 F Degrees.
Put eggs, heavy cream, butter, Frangelico, vanilla extract, and sugar into a medium-mixing bowl. Whisk until smooth. (I did by hand, but if you want you can use a mixer.)
In a separate bowl, combine flour, baking powder, and salt.
Gently, whisk the dry ingredients in to the wet ingredients, until combined and there are no lumps remaining.
Fill a piping bag with Nutella. Set aside.
Spray a 10-inch pie pan with butter and flour spray.
Arrange half of the sliced bananas, in a single layer, in to the pie pan. Pour half of the batter over the bananas.
Pipe the Nutella all over the batter (for more, see the video).
Pour the rest of the batter over the Nutella, making sure that it is all covered.
Arrange rest of the bananas on top, and sprinkle it generously with roasted hazelnuts.
Using a rubber spatula, smooth the surface of the batter.
Bake it for 30-35 minutes, until the top is golden brown and the custard is firm.
Allow it to cool in room temperature, for at least 30 minutes.
When cooled, if you’d like, dust it with cocoa powder and powdered sugar.