Preheat the oven to 250 degrees Celsius (482 degrees Fahrenheit) fan.
Put eggs and sugar in a bowl and whisk until airy and white.
Sift potato flour, cocoa, and baking powder into the egg mixture and fold together gently.
Pour the batter onto a baking sheet lined with baking paper and spread it in a thin layer, like for a roulade.
Bake the batter in the middle of the oven for 5 minutes.
Turn the cake layer over onto a damp tea towel to cool.
When the cake is cool, divide the batter into two pieces.
Put ice cream on one cake layer and then place the other cake layer on top.
Divide the cake into 8-12 pieces, depending on the desired size and shape of the sandwich ice cream.
Put the sandwich ice cream in the freezer for at least 2 hours, preferably overnight.
