Preheat oven to 350F.

Line a 9" springform pan with parchment, then grease.

In a medium bowl, beat the egg whites until stiff peaks form. Set aside.

In a large bowl, beat the butter and sugar until fluffy. Add in the vanilla extract and the egg yolks, one at a time. Beat until well blended.

In another medium bowl, mix the flour, cocoa powder, baking powder, hazelnuts,and grated chocolate.

Mix half the dry mixture into the butter and beat until incorporated. Add the second half of the dry mixture and mix well.

Gently fold in the egg whites, one third at a time.

Scrape batter into prepared pan and bake 40 minutes on the middle rack, or until a wooden skewer inserted into the middle comes out clean.

Let cool on a wire rack. Remove from pan and set aside. This can be done up to one day in advance.

In a large bowl, beat the cream, sugar, vanilla, and Whip It until stiff peaks form. Set aside.

Hollow out the inside of the cake, leaving about 1-2 cm of cake on the bottom and sides. Reserve the crumbs and set aside.

Peel and slice the bananas lengthwise. Arrange the banana halves evenly in the cake hollow.

Mound the whipped cream over the bananas; do not level the whipped cream but leave it mounded tall.

Sprinkle and gently press the reserved cake crumbs evenly over the whipped cream.

Let chill for 1 hour before serving.