1. Preheat a fan forced oven to 160C. Line 2 baking trays with canola oil and baking paper.
  2. Using an electric mixer, cream the butter and sugar until light and fluffy. Add 1 tablespoon of boiling water and continue to beat on a high speed for 1 minute.
  3. Fold through the flours and then roll into 2 teaspoon sized balls. Place onto the baking trays 5cm apart and lightly press down with a fork. If the fork sticks, dip it into a little bit of corn flour. 
  4. Cook for 15 minutes or until they just begin to brown. Allow to cool on cake racks.
  5. To make the icing, beat the passionfruit and icing until it is thick and lightened in colour. If the mixture needs it, you can add 1 teaspoon of boiling water at a time. The icing needs to be quite thick so do not add too much liquid.
  6. Scoop icing into a piping bag with a .5cm tip and pipe roughly 1 teaspoon of icing onto half of the cookies. Top with another cookie and allow to set. Store in an airtight container for up to 7 days.