1.Preheat oven to 180°C (160°C fan forced). Line 2 baking trays with baking paper.
2.Using an electric mixer, beat butter, sugar, passionfruit and essence in a medium bowl until pale and creamy. Sift flours over butter mixture. Using a wooden spoon, stir to combine.
3.Roll rounded teaspoons of dough into balls. Place on prepared trays. Using the palm of your hand, slightly flatten each ball into 3.5cm rounds. Using a floured fork, press gently into dough rounds to create grooves. Bake for 12 minutes or until light golden. Cool on trays for 5 minutes; transfer to a wire rack to cool completely.
4.Make passionfruit icing. Sandwich biscuits together with 1-2 teaspoons of icing.
5.Using an electric mixer, beat butter, sifted sugar and passionfruit in a small bowl until pale and creamy.
We used canned passionfruit pulp in syrup; you can use fresh passionfruit pulp when in season. Try flavouring biscuit mixture with orange or lemon zest. Have all ingredients at room temperature before you start. Place biscuits 4cm apart on prepared trays to allow for spreading. Tint icing using a few drops of colour at a time. Colour will intensify.