Preheat oven to 180?C. Line 2 baking trays with baking paper. Place butter, sugar and vanilla into a food processor. Process for 2 minutes or until well combined.

Add flour and custard powder. Pulse until just combined (don't over-process or biscuits will not have a fine texture).

Roll heaped teaspoonfuls of mixture into small balls. Place onto prepared baking trays. Press with a floured fork to flatten slightly. Bake for 12 minutes or until light golden. Allow to stand on trays for 2 minutes before transferring to a wire rack to cool. Repeat with remaining biscuit mixture.