Start by lining baking trays with baking parchment and put aside. Preheat oven to 170°C. Place the butter substitute, sugar and vanilla essence into a mixing bowl and cream until light and fluffy. Sieve in the flour and corn flour then carefully mix to a smooth paste. Wrap the pastry in cling film and refrigerate for 1 hour before rolling. Remove from the fridge and roll out using pastry cutters to cut the shortbread into discs. You can also cut the shortbread into think fingers and prick the top with a fork. Place on to prepared trays and bake at 170`c for approximately 20 minutes, or until just turning golden brown at the edges. Remove and sprinkle with cater sugar, allow to cool on trays. You may also sprinkle over a little cinnamon. Allow to cool before serving.