Abruzzese sweet layered cake with sponge, custard, and chocolate is a celebration essential. This rich mediterranean dessert is a family tradition for weddings and holidays.
Preheat the oven to 350°F (175°C). Line a 9-inch cake pan with parchment and lightly grease it.
Beat 6 eggs and 1 cup sugar at high speed for 6-7 minutes until pale and thick, then gently fold in 1.5 cups flour and lemon zest with a spatula.
Pour the batter into the prepared pan; bake for 22–25 minutes, checking with a toothpick (should come out dry). Cool completely before unmolding.
Meanwhile, make the custard: Heat 2 cups milk in a saucepan until steaming. In another bowl, whisk 3 eggs, 0.5 cup sugar, 0.5 cup flour, and a pinch of salt until smooth. Gradually add the hot milk, whisking constantly, then transfer back to pan and cook over medium heat, stirring, until thickened. Remove from heat, add 1 tsp vanilla and 2 tbsp butter, and cool.
Set aside half the custard. Melt 6 oz chocolate with 0.5 cup milk and 2 tbsp butter, stir into remaining custard to make chocolate filling. Chill both fillings for 30 minutes.
Slice the cooled sponge cake horizontally into 3 layers. Brush each with a mix of 2 tbsp rum and 0.5 cup milk to moisten.
Assemble: Place one layer on a platter, spread with plain custard. Add the second layer, spread with chocolate custard. Top with the final layer and gently press.
Refrigerate cake for at least 4 hours (or overnight) for best flavor and structure. Dust with powdered sugar before serving if desired.