Method

• 1.
  For the cookies, combine flour, baking powder and ½ tsp fine salt in a medium bowl. Give these dry ingredients a good whisk and set aside. Using a stand mixer fitted with the paddle attachment, mix caster sugar and zest on medium speed – this will help release the grapefruit oils into the sugar, giving an even more vibrant flavour. Add butter, egg yolk and vanilla and mix until thoroughly combined but not aerated (we don’t want the cookies to spread too much). Finally, add the dry ingredients and mix until a soft dough forms. Wrap the dough in biodegradable plastic wrap and refrigerate for 1-2 hours. This will also ensure that the biscuits don’t spread too much while baking.
• 2.
  Preheat oven to 200°C/180°C fan-forced and line 2 baking trays with baking paper or silicone baking mats.
• 3.
  Lightly dust a work surface with extra flour. Using a rolling pin, roll out chilled dough to 3-4mm thick. Using a fluted 5cm round cookie cutter, cut out 36 rounds and arrange on prepared trays, with 2-3cm between. Bake for 12-15 minutes, until the cookies look dry all the way to the centre but are still blond. Transfer to a wire rack to cool completely while you make the filling.
• 4.
  For grapefruit cream, combine all ingredients in a stand mixer fitted with the whisk attachment. Whisk on medium speed until cohesive and aerated – it will appear to split because of the juice, but keep mixing until it comes together. Spoon cream into a piping bag fitted with a 1cm star nozzle.
• 5.
  Pipe 1-2 tsp of cream in centre of half the cookies and sandwich with remaining cookies. Lightly dust with icing sugar.