Torta alla Giundia Recipe

From How to Be a Domestic Goddess by Nigella Lawson:

Ingredients
6 large eggs separated
pinch of salt
1/2 cup unsalted butter
14 oz. nutella jar (resist the temptation to eat it all ...)
1 tbsp. frangelico (I doubled this)
1/2 cup ground hazelnuts (I had much less actually)
4 oz. bittersweet chocolate melted
9" springform pan lined with greased wax paper (I found a greased cake pan worked fine)

Icing
4 oz. hazelnuts
1/2 cup heavy cream (here I used half and half with some cooled hazelnut-flavored espresso mixed in to give the icing an extra touch)
1 tbsp. frangelico (again I just eyeball it)
4 oz. bittersweet chocolate (I was a bit short so I supplemented a bit of semi-sweet)

Directions
1) Preheat oven to 350 degrees. Whisk egg whites in large bowl, with pinch of salt, until stiff but not dry. (Be patient here!)
2) In a separate bowl beat the butter and nutella until creamy. Add frangelico, egg yolks, ground nuts and blend.
3) Melt bittersweet chocolate over double boiler and cool. Fold cooled melted chocolate into batter.
4) Add a dollop of egg white, about a third, and fold in, and repeat with remaining thirds. Do not overstir.
5) Pour into pan, bake 40 minutes, cool on rack.
6) Toast hazelnuts and cool totally for cake topping.
7) To make the icing: in heavy-bottomed pan add cream, chocolate, liquer, and heat gently until melted. Remove from the heat and whisk smooth. Cool.
8) Frost the cake with icing and top with toasted hazelnuts. Serve.