Pan di Spagna (Sponge Cake)
6 eggs, separated
220g caster sugar
finely grated zest of 1 lemon
1 cup sifted flour
pinch salt

For the filling
160g best-quality dark chocolate
1/2 cup each almonds and hazelnuts, roasted and coarsely chopped
1 cup mixed candied fruit (I used halved Amarena cherries, diced candied orange and diced citron, but while not traditional, sliced prunes, apricots, sticky raisins or even fresh dates would do as well)
500mls cream, whipped lightly

To assemble
1/2 cup rum or maraschino liqueur
cocoa for dusting

This is the dome-shaped cake which is said to resemble both the dome of the world-renowned cathedral in Florence, the Duomo, and a zucchetto (zuccotto in Tuscan dialect), the skullcap worn by certain Roman Catholic clergy.

Method
Pan di Spagna (Sponge Cake)
Preheat the oven to 180°C. Brush a 25cm-diameter springform cake tin lightly with melted butter and then dust with flour.

Beat the egg yolks, sugar and lemon zest in an electric cake mixer or with a whisk until very thick and pale. Beat the egg whites until stiff but not dry and fold half of them into the yolk mixture, followed by the other half.

Add the flour and salt and carefully fold them into the mixture. Pour into the tin and bake 30 minutes in the oven or until a skewer inserted into the middle comes out clean. Remove sponge cake from the oven and cool completely.

For the filling
Melt half the chocolate and finely chop the other half.

Fold the chopped chocolate, nuts and candied fruit into the cream and divide the mixture into 2 equal portions.

Fold melted chocolate into 1 portion of the cream.

To assemble
Preline a 22cm-diameter x 10cm-deep bowl with plastic wrap.

Slice the sponge cake horizontally into 3cm-thick slices and then neatly line the bowl, making sure to leave enough cake slices to cover the top once the inside is filled with the cream mixtures.

Brush the cake lining well with the rum or maraschino. Cover cake lining evenly with a thick layer of the white cream mixture leaving a cavity for the chocolate mixture.

Pile chocolate cream into the cavity and smooth the top. Cover with the remaining cake slices.

Brush the top with the remaining rum or maraschino. Cover with plastic wrap, weight lightly with a couple of dinner plates and refrigerate overnight.