Pre-heat the oven to 160C (320F) and line a baking tray with baking paper.

In the bowl of an electric mixer, add the butter, icing sugar and cumquat rind and beat until light and fluffy (you may need to scrape the sides at some point).

Sift the flour and cornflour together and add to the bowl and mix just until it comes together.

Using about a teaspoon of dough at a time, roll it into balls and place on the trays leaving a couple of centimeters between each one.

Use your hand to press the biscuits down then dip a fork in water and make an indent in the top of each one, re-dipping every time.

Bake the biscuits for 15 minutes or until lightly golden.

Leave on the tray for 5 minutes and then transfer to a wire rack to cool completely.

To make the icing, beat the butter, cumquat juice and rind until light and creamy then sift in the icing sugar and beat until light and fluffy.

Pair up your biscuits so they all have a partner roughly the same size then turn one over onto its head. Spread the upside down biscuits with icing and sandwich the mate on top.

Dust the biscuits with icing sugar.