• 175 g (6 oz) unsalted butter
• 250 g (9 oz/1⅔ cups) plain (all-purpose) flour
• 60 g (2¼ oz/⅓ cup) rice flour
• 1 teaspoon baking powder
• ½ teaspoon salt
• 125 g (4½ oz) caster (superfine) sugar
• 80 g (2¾ oz/½ cup) macadamia nuts, chopped

Preheat the oven to 180°C (350°F/Gas 4). Line a 20 cm (8 inch) square slice tin, about 4 cm (1½ inch) deep, with baking paper.

Remove the butter from the refrigerator 20 minutes before using. Sift the plain flour, rice flour, baking powder and salt into a bowl. Add the caster sugar and stir to combine.

Cut the butter into 1.5 cm (⅝ inch) cubes and use your fingertips to gently rub the butter into the dry ingredients, until the mixture resembles breadcrumbs. Add the macadamias and continue rubbing together to combine, and then knead to form a dough.

Pat the mixture into the prepared tin and smooth the top using the back of a spoon, making sure it is even all over. Place in the refrigerator for 20 minutes to rest.

Bake in the oven for 30–40 minutes, or until the shortbread is light golden and firm to the touch. Allow to cool in the tin before turning out and cutting into fingers with a serrated knife. Shortbread can be stored in an airtight container for up to 5 days.