Swap passionfruit pulp for any citrus juice, or leave biscuits uniced and sandwich with caramel filling.
220g unsalted butter, chopped, softened, plus extra 2 tsp, melted
1⁄2 cup icing sugar mixture, plus extra 1 cup
2 1⁄2 cups plain our
2 1⁄2–3 Tbsp fresh passionfruit pulp
Preheat oven to 160°C fan- forced (180°C conventional). Line 4 oven trays with baking paper. Put butter and sugar in a large bowl and beat on high, using an electric hand mixer, for 2 minutes or until pale and fluffy. Add flour and mix with a wooden spoon until mixture forms a soft crumbly dough. Keep mixing until a smooth dough forms.
Roll out dough between 2 sheets of baking paper until about 8mm thick. Use 4cm, 5cm and 6cm heart- shaped biscuit cutters to cut shapes from dough, rerolling as necessary.
Arrange on prepared trays 2cm apart. Bake, 2 trays at a time, for 16 minutes or pale golden brown and firm to touch. Set aside on trays to cool completely.
Meanwhile, put extra butter and icing sugar in a large bowl and stir in passionfruit pulp until smooth.
Spread a little icing on each cooled shortbread. Set aside until icing sets. Serve.