I found this recipe in the AWW Cakes, biscuits and slices. While baking I also noticed the exact same recipe is on the CSR brown sugar packet.
3/4 cup firmly packed brown sugar (the recipe called for dark brown sugar, but I only had the normal one on hand)
1 cup cornflour
1 tsp cream of tartar
1/2 tsp bicarb of soda
300ml thickened cream
1. Preheat oven to 180degC (160 fan-forced) and prepare two 22cm round baking tins
2. In a large bowl, beat eggs and brown sugar with electric mixer for about 10 mins or until thick and creamy.
3. Sift cornflour, cream of tartar and bicarb of soda twice. Sift a third time into the egg and sugar mixture then gently fold.
4. Divide the mixture between the two cake tins.
5. Bake for 15-18 minutes. Turn out sponges onto baking paper covered wire racks to cool.
6. Beat cream until soft peaks form.
7. When cake is completely cool, spread half of the cream on top of one cake and lay the other cake on top. Spread the remaining cream on top.