Line a baking sheet with parchment paper. Preheat the oven to 200 degrees top / bottom heat or 175 degrees circulating air.
Mix cornstarch and baking powder. Add the oil, sugar and eggs and then beat with the food processor for about 5-6 minutes. The sugar should dissolve.
Pour the very liquid batter onto the baking sheet and bake for 15 minutes.
If you need the springform-sized biscuit for a cake, use the cake ring to cut the right size out of the cold base. Use leftover biscuits e.g. for a tiramisu.
For a chocolate biscuit you only use 170 g of corn starch and add 10 g of heavily de-oiled cocoa powder. The vanilla sugar is replaced by normal sugar.