Prep Time: 18 minutes (8 hours INACTIVE prep time)
Cook time: 20 minutes
Serves: 6 to 8
An utterly decadent dessert. Serve as a wrap-up to a fancy dinner party or if you're just in the mood for something rich and chocolaty!
- Nonstick cooking spray
- 3 plain or almond biscotti, halved (around 4 oz., make sure they're the 5" long by about ¾" wide size)
- ¼ cup toasted hazelnuts 
- 4 tbsp unsalted butter, melted
- 8 egg yolks at room temperature
- ½ cup sugar, plus ¼ cup
- 1 tsp pure vanilla extract (no imitation)
- ⅛ tsp fine sea salt
- 1 cup heavy cream
- ¾ cup Nutella at room temperature
Special equipment: 2 pieces of parchment paper, cut into 3" x 15" and 7½" x 12", respectively
- Place an oven rack in the center of the oven. Preheat the oven to 350 °F. Spray a 9 x 5" loaf pan with the nonstick cooking spray and line the pan using the parchment paper, letting the excess hang over the edges. This will form "handles" that will make it easy to lift the semifreddo out of the pan when it's time to serve it.
- In a food processor, blend the biscotti and hazelnuts together until finely ground. Add the melted butter and pulse until the crumbs are moistened.
- Using a flexible spatula, press the crumbs into the bottom of the pan. Bake 8 to 10 minutes until the edges of the crust are golden. Let the pan cool on a wire rack for 20 minutes.
- In a medium stainless steel or glass bowl, whisk together the egg yolks, ½ cup sugar, vanilla extract and salt until smooth.
- Put the bowl over a simmering pan of water, making sure the bottom of the bowl does not touch the water (if it does, your egg mixture will curdle and you will have to start all over again). Whisk until the egg mixture is pale, thick and creamy. Test with an instant-read thermometer; the mixture should reach around 160 degrees, which should take between 10 - 15 minutes of constant cooking/whisking. Put the bowl into a larger bowl of ice water to help the mixture cool completely.
- In another bowl, using an electric hand mixer (or a Kitchenaid), beat the cream until thick. Add the remaining ¼ cup sugar and beat until the cream holds stiff peaks. Mix ¼ of the cream into the cooled custard.
- Using a spatula, gently fold the remaining cream into the custard. Drop spoonfuls of the Nutella into the custard mixture and gently fold, but do not mix in completely; the Nutella should remain somewhat chunky. Spoon the mixture into the prepared crust. Fold the overhanging parchment paper over the top and freeze for at least 8 hours or up to 3 days.
- Run a thin bladed spatula around the edge of the semifreddo between the parchment paper and the pan. Unfold the paper and invert the semifreddo onto a serving plate/platter. Peel off the paper carefully and cut into 1" thick slices. Serve immediately on chilled plates.
- A good beverage accompaniment for this dessert is a small cup of espresso or a regular cup of coffee.
- Cook's Note: To toast the hazelnuts, arrange in a single layer on a cookie sheet. Bake in a preheated 350 °F oven for 8 to 10 minutes until lightly toasted. Cool the nuts completely before using.