Ingredients

2 cups all-purpose flour
1/2 cup unsweetened cocoa
1 tsp. baking powder
1/2 tsp. baking soda
1 tsp. salt
6 large eggs
3/4 cup sugar
1 tsp. vanilla extract

Instructions

Preheat the oven to 375°F. Grease and lightly flour a 10" cake pan with sides 3" high.

Sift together the flour, cocoa, baking powder, and baking soda. In a medium bowl set over a pan of simmering water, beat the eggs and sugar together until the mixture has warmed and most of the sugar has dissolved, about 3 minutes. Using a hand-held electric mixer, beat the egg-sugar mixture at high speed until doubled in volume, about 5 minutes.

Off heat, fold in the sifted dry ingredients, pour the batter into the prepared cake pan, and bake about 25 minutes, until a tester inserted into the center of the cake comes out clean and the cake's surface springs back when lightly pressed. Cool completely for 2-3 hours.

For the syrup:
1/2 cup limoncello liquor
2 Tbsp. Confectioners' sugar

Warm the limoncello in a saucepan and whisk in the sugar until dissolved.

For the filling:
1 tsp. unflavored gelatin
1/4 cup plus 1 1/2 Tbsp. cold water
1/3 cup plus 1 Tbsp. sugar
7 egg yolks (at room temperature)
1/2 lb. semisweet chocolate, chopped
1/4 cup limoncello
1 1/2 cups heavy cream, whipped until stiff
3 Tbsp. melted chocolate

In a small saucepan, soften the gelatin in the 1 1/2 tablespoons cold water. In a medium size heavy saucepan, combine the sugar with the 1/4-cup of water and bring to a boil over moderately high heat. Cook until the resultant syrup registers 240°F. on a candy thermometer or forms a soft ball when dropped into cold water, about 5 minutes.

Meanwhile, beat the egg yolks in a stainless steel bowl. Set the bowl over a pan of lightly simmering water and heat until warmed through but not cooked. Beat in the sugar syrup until well blended, and remove from the heat.

Melt the softened gelatin over low heat until completely dissolved. In a small bowl set over a pan of gently simmering water, melt the chocolate until smooth but not hot. Beat the chocolate into the egg sugar mixture, then beat in the dissolved gelatin and the limoncello. Fold in the whipped cream until no traces of white are visible.

Assembling the cake:
Using a long, serrated cake knife, slice the chocolate sponge cake horizontally to form three layers of equal thickness.
2. Set the bottom layer into a 10" springform pan and brush the surface with Limoncello syrup, moistening it well. Spoon 1/3 of the filling over the surface, and repeat all steps with the remaining two layers of sponge cake, ending with filling to cover the surface of the top layer. smooth with a spatula, cover, and refrigerate overnight.

Remove the cake from the springform pan and sprinkle with slivered almonds. Serve in slices with hot Chocolate Zabaglione sauce.

Chocolate Zabaglione Sauce
6 egg yolks (at room temperature)
1/4 cup dry limoncello
1/4 cup sugar
3 oz. semisweet chocolate chopped and melted.

In a large saucepan, bring 3" of water to a simmer. In a copper or stainless steel bowl, whisk together the egg yolks, limoncello, and sugar.

Set the bowl over the simmering water and whisk constantly until the mixture is fluffy, light, and hot, 3-4 minutes.

Off the heat, very slowly and thoroughly fold in the melted chocolate. Spoon hot sauce over cake.

Note: This sauce must be made just before it is served.