Preheat the oven to 170C / 340F. Line a 2 x 20 cm or 8 inch tins with parchment paper bottom and sides. You will need either a handheld or a stand mixer for this recipe
Sieve the flour, cornflour, salt and baking soda, cream of tartar together and mix well
Use a mixer for the next step. Make sure the bowl and whisks are very clean. Add the egg whites (4 x 30 gm = 120 gm) and whisk on a high speed until the whites have started to become white and frothy and are just starting to become soft peak. Gradually add the sugar in 3 to 4 additions. The whites will be stiff peaked shiny.
Once the whites are nice and shiny, add the yolks (20 gm x 4= 80 gm approx) one at a time until the 4 have been incorporated. The mixture will be very creamy thick and pale.
Pour the mixture into a large bowl. Sift 1/3 of the flour onto the egg mixture and use a spatula fold through, continuing until all the flour is incorporated. Mix ONLY until just mixed in. Do not overmix.
Decant into the two cake tins and flatten the top. Bake for 20 to 25 minutes or until the sponge springs back when touched in the centre. When cooked sit on a cooling rack for 10 minutes before running a knife around the edge to loosen then turning out.