Method

1. To make the biscuits, beat butter, icing sugar, lime juice and vanilla paste with
   an electric mixer for 3 minutes, until pale and creamy.
2. Sift flour and cornflour over the butter mixture and stir with a wooden spoon
   until well combined. Refrigerate 10 minutes to firm up slightly.
3. Preheat oven to 160°C and line two oven trays with baking paper.
4. Roll a heaped tablespoonful of dough into a ball, place on lined tray and press
   lightly with the tines of a fork to form a cross-hatch pattern on the top. Repeat
   with remaining dough to make 24 biscuits.
5. Bake approximately 14 minutes until just golden. Cool briefly on trays,
   then transfer to a wire rack to cool completely.
6. To make lime butter, beat all ingredients with an electric mixer for
   3 minutes until pale and creamy.
7. Top half the biscuits with lime butter and refrigerate 15 minutes to firm up.
   Top lime butter with a spoonful of cooled passionfruit curd and sandwich with
   remaining biscuits. Store sandwiched biscuits in an airtight container in the
   refrigerator for up to 3 days.