Begin by making the zabaglione filling. For this you need to take a medium-sized bowl and in it beat the egg yolks for 1 minute with an electric hand whisk, then add the sugar and whisk again until the mixture turns thick and pale – about 3 minutes.
After that, add a tablespoon of flour at a time and continue whisking till everything is smooth and creamy, then gradually whisk in the Marsala.
Next transfer the mixture to a medium-sized saucepan and place it over a medium heat, then take a wooden spoon and keep stirring the mixture until it has thickened and is just about to come to simmering point.
This usually takes about 5 minutes.
Don’t worry if it overheats and begins to separate, just remove it from the heat and keep whisking until it is smooth again.
Transfer the mixture to a bowl, cover the surface of the mixture with clingfilm to stop a skin forming and leave it to get completely cold.
Then pop it in the fridge till needed.
To make the cake, begin by pre-heating the oven to 170°C, gas mark 3.
Then sift the flour and baking powder into a large roomy bowl, lifting the sieve high to give the flour an airing.
Now just add all the other ingredients (apart from the icing sugar) and, using the electric hand whisk, whisk for about one minute until you have a smooth creamy mixture that drops off a spoon easily.
Next, transfer the mixture into the tin, levelling it with the back of a spoon, and bake near the centre of the oven for 30–35 minutes or until the centre feels springy.
Leave the cake in the tin for 5 minutes before loosening the edge by sliding a palette knife all round and turning it out onto a cooling rack.
Now peel off the base, place another rack on top and flip it back over, then let it get quite cold.
To serve the cake, first whisk the zabaglione mixture to loosen it, then in a large bowl whisk the cream till stiff and fold in the zabaglione. Next you need to place the cake on a flat surface and, using a serrated palette knife, carefully slice it horizontally into two thin halves.
Keep aside 2–3 heaped tablespoons of the zabaglione to decorate the sides, then spread the rest over one half of the cake and place the other half on top, pressing it down gently.
Now carefully transfer the cake to a serving plate. Brush away any loose crumbs then, using a small palette knife, spread the rest of the filling all around the sides of the cake, and use the palette knife to make a vertical pattern, sliding the knife upwards from the base.
Finally, dust the top of the cake with icing sugar.
If you want to make this ahead of time, cover the cake with an upturned bowl and keep in the fridge (but remove it 30 minutes before serving).