In a saucepan combine the milk, cream and 1/3 cup sugar over medium heat.  Cook until the sugar dissolves.

Meanwhile, in a medium bowl beat the egg yolk with the remaining 1/4 cup sugar until eggs are thick and pale yellow.  Slowly add about 1 cup of the hot milk mixture into the egg mixture and stir.  Pour the egg mixture back into the pan with the remaining milk mixture and continue to cook until the mixture becomes thick and coats the back of a spoon.

Place a strainer over a medium bowl and pour the warm custard mixture through the strainer.  Stir in the vanilla and hazelnut paste and stir until smooth.  Cover and refrigerate until mixture is completely cold.  When mixture is cold pour into a ice cream maker and freeze according the manufacturers directions.

When gelato is almost complete add chopped hazelnut candy (Ferrero Rocher)

Preheat oven to 350F degrees. Spray a baking 12 x 17-inch baking sheet with non-stick spray.  Line with a sheet of parchment paper and spray paper.  Set aside.

In a small saucepan heat butter, water and cocoa.  Stir until smooth and butter is completely melted.

In a large mixing bowl mix sugar, flour and salt together.  Add the warm butter mixture and mix until smooth. Beat in eggs, buttermilk, vanilla baking soda.

Pour into prepared pan and bake for 30 minutes.  Remove from oven and cool 5 minutes.  Turn cake out onto a wire rack, peel off parchment paper and cool completely.

Heat cream in a small saucepan until it begins to bubble around the edges.  Pour hot cream over chocolate and let stand for 5 minutes.  Stir until smooth.

Line a 8 x8-inch pan with parchment paper having the ends drape over the sides of the pan.  Cut two pieces of the cake that are 8 x 8 the size of the pan.  Place one piece on the bottom of the pan.  Spread the frozen gelato over the top of the cake.  Add second 8 x 8 inch cake piece over the top of the ice cream and press down firmly.  Cover with plastic wrap and freeze until very firm.

When completely frozen remove from freezer and spread warm ganache over the top cake layer.  Sprinkle with hazelnuts.  Return to freezer until the ganache is set.  Remove from pan and cut the cake in half.  Cut each half into 6 slices, about 1 1/2-inches.