Syrup
1/2 cup granulated sugar
1/2 cup water
6 tablespoons dark rum

Filling
1 (13 ounce) jar Nutella
1 1/2 cups heavy whipping cream, divided
1 teaspoon vanilla extract
1 recipe Sponge Cake (Pan di Spagna)

Glaze
1 cup heavy whipping cream
2 tablespoons unsalted butter, at room temperature
12 ounces semisweet chocolate, chopped

Syrup: Combine the sugar and water in a small saucepan, bring to a boil, and boil until the sugar is dissolved and the mixture is reduced by one-quarter. Let cool, and stir in the rum.

Filling: In a small bowl, whisk the Nutella with 1/2 cup of the cream to lighten the Nutella. In a mixing bowl, whip the remaining 1 cup cream with the vanilla extract until it begins to hold its shape. Add the Nutella mixture and continue to whip until stiff.

To Assemble the Cake: Line a 10-inch springform pan with plastic wrap. Cut the sponge cake into three 1/2-inch layers. Place 1 cake layer in the bottom of the pan, brush with one-third of the rum syrup, and spread evenly with half the filling. Repeat with another layer of cake, another one-third syrup, and the remaining filling. Finish with the final cake layer and the remaining syrup. Chill, covered, for 2 hours before unmolding.

Meanwhile, make the Glaze. Bring the cream and butter just to a boil and immediately remove from the heat. Add the chocolate and let sit for 5 minutes to allow the chocolate to melt, then whisk until smooth. This glaze solidifies significantly upon cooling; if it becomes too stiff to work with, warm it over low heat, stirring carefully.

Invert the cake onto a serving platter and remove the pan and plastic wrap. Pour or spread the glaze evenly over the top and sides of the cake. Allow the glaze to set before serving.

Makes 10 to 12 servings.

Sponge Cake (Pan di Spagna)
6 eggs, separated
3/4 cup granulated sugar, divided
1 tablespoon hot water
1 teaspoon vanilla extract
Grated zest of 1 lemon
1 1/4 cups cake flour *
1/2 teaspoon baking powder
1/4 teaspoon salt

* If cake flour is unavailable, substitute 1 cup unbleached all-purpose flour and 1/2 cup cornstarch. Sift both the flour and cornstarch well before measuring.

Preheat the oven to 350 degrees F. Line the bottom of a 10 x 3-inch springform pan with wax paper or baking parchment.

In a large bowl, with an electric mixer, whip the egg yolks with 1/2 cup of the sugar, the water, vanilla extract and lemon zest until light yellow and tripled in volume.

Sift the flour, baking powder, and salt directly onto yolk-flour mixture and gently fold in.

In a separate bowl, with clean beaters, whip the egg whites until soft peaks form. Whip in the remaining 1/4 cup sugar, a tablespoon at a time, until stiff peaks form. Fold the whites gently but with authority into the yolk-flour mixture until no white streaks remain.

Spread the batter evenly in the prepared pan and bake for 35 to 40 minutes, or until the cake is golden brown and the top springs back when lightly touched. Set upside down on a cooling rack and cool completely before removing from the pan.

Makes one 10-inch cake.