As you can see, potato flour is pure white in colour, very finely textured, it's like a cross between icing sugar and pure cornflour. For those with gluten intolerance, you'll be happy to know that this is gluten free.
Torta Margherita is one of the cakes my mother would reserve for special occasions. It is as light as a sponge but has a fascinating, almost chewy crust and great mouth-feel which I can only credit as a property of potato flour.
150 grams caster sugar
120 grams potato flour
finely grated rind of 1 lemon
The most important part in making Torta Margherita is ensuring that the eggs and sugar have been whipped correctly - you can't rush this and as my mother tells me, back in Italy without the benefit of electric mixers, this process would take a good 30-40 minutes to do by hand.
Place the eggs and sugar into the bowl of a stand mixer and beat until thick and creamy. Stop after about 5 minutes to add the grated lemon and then continue beating for another 5 minutes. In my Kitchen Aid bowl, this reached almost to the top of the bowl.
Double sift the potato flour and on a low speed sprinkle in the flour - once it has all been added, increase the heat and whip for 10-15 seconds to ensure the flour has been dispersed.
Pour the mixture into a buttered and lined cake tin - I used a 23cm spring-form pan but you could divide the mixture to make 2 x 18cm cakes.
Bake in a preheated 160°C/320°F oven until golden and cooked through. Much like a souffle this will rise will cooking.
Cool slightly before removing it from the pan and then dust with icing sugar.
This is a very simple version - split it and fill it with crema pasticcera for a more decadent option.