Pan di Spagna:

1. Butter and flour a 24cm springform pan. Preheat the oven to 350° F (180° C).
2. In the bowl of a stand mixer, whisk the eggs with the sugar.
3. Place the bowl over a double boiler (bain-marie). Whisking constantly, heat the mixture on medium heat and with a thermometer, bring it to a temperature between 45° and 50° C. The heat allows the eggs to absorb more air and the sugar to melt faster.
4. Once at temperature, move the bowl to the stand mixer and whisk for 20 minutes at a low/medium speed (4 on the KitchenAid). They will triple in volume and be light and fluffy. Just before the end add the lemon zest.
5. Sift the flour twice and divide it into two parchment papers. With the stand mixer still on low/medium speed, add half of the sifted flour, mix 3 seconds at high speed than lower the speed back to 4. Add the second half of the sifted flour, and repeat (high speed for 3 seconds, then back to low), mixing just until combined. Do not overmix. [If you prefer, you can add the sifted flour to the egg mixture folding gently with a spatula with movements from bottom to top.]
6. Pour the batter into the prepared pan, leveling the top gently with a spatula.
7. Bake at 350° F (180° C) for 25-30 minutes. or until lightly golden.
8. Take out of the oven and cool on a rack, then unmold and place it upside down on the rack to cool completely. Wrap it in plastic wrap until ready to use the next day.

Custard:

1. In a thick-bottomed saucepan, simmer the milk with a vanilla bean pod for about 5 minutes, then turn off and set aside. Remove the bean pod (let dry, you can use it again).
2. Whisk the egg yolks with the sugar in a bowl. Add the cornstarch and continue mixing until a smooth.
3. Now pour the warm milk over the egg mixture slowly while mixing, then pour it back in the saucepan.
4. Cook the custard on low heat, stirring constantly so as not to create lumps. When the custard begins to thicken, turn off the heat and mix vigorously with a whisk or a wooden spoon.
5. Pour custard into a sieve and with a spatula push it through. It will get rid of any lumps.
6. Divide the cream into two bowls, in one sieve the unsweetened cocoa and stir until a smooth chocolate custard is obtained. Let cool.

Assembly:

1. Take the sponge cake and using a serrated knife divide it into three equal horizontal layers.
2. Take the first layer of sponge cake and place it on the serving dish where you have poured some Amarula Cream Liqueur. The liqueur will soak the bottom of the sponge making it softer. Then, brush more Amarula Cream Liqueur on top of the first layer.
3. Distribute evenly the chocolate custard on the first layer.
4. Place the second layer of sponge cake on top, press a little, and brush generously with Amarula Cream Liqueur.
5. Spread a layer of custard, setting aside 1/4 of the custard for the top of the cake.
6. Place the third and last layer of sponge cake on top, press a little, brush with more liquor and spread the custard you have kept aside.
7. Dust the top with chocolate shavings and set in the fridge to rest for at least 4 hours (the days after the Zuppa Inglese will be even better!)
8. Serving suggestions: you can add some more chocolate shavings on top before serving. Serve a slice of Zuppa Inglese cake with some Amarula butter on the side.

Amarula butter:

1. In a medium-size bowl, add the soft butter, then cream it using a handheld mixer, or a stand mixer.
2. Add the sugar, maple syrup, and rum and beat everything together.
3. Grate in nutmeg, add the pinch of cardamom, and mix again.
4. Place in a bowl or a jar, and chill until required.