A sophisticated and dainty take on an elevenses classic, these custard creams are made with pistachio-dotted biscuit dough and filled with jam and buttercream.
Make the biscuit dough. Beat together the butter and sugar in a stand mixer fitted with the beater until pale and creamy. Add the custard powder and flour and mix with a wooden spoon to a soft dough. Fold in the pistachios until evenly distributed.
Using your hands, bring the dough together, then wrap in cling film and chill for 20 minutes, until firm.
Meanwhile, spoon the jam for the filling into the small piping bag fitted with a plain nozzle and set aside.
Make the buttercream. Beat together the butter and icing sugar in a stand mixer fitted with the beater until smooth. Spoon into the medium piping bag fitted with a plain nozzle. Set aside. Heat the oven to 180°C/160°C fan/350°F/Gas 4.
Remove the dough from the fridge. Place it on a sheet of baking paper and place another sheet of baking paper on top. Roll out the dough between the sheets of baking paper until 3mm thick. Remove the top sheet of baking paper.
Using the 3.5cm square cutter, cut out 24 squares of biscuit dough (re-roll the trimmings if necessary). Gently transfer the squares to the lined baking sheet, then place in the fridge to chill for 10 minutes.
Once chilled, bake the biscuits for 15–18 minutes, until pale and golden. Remove from the oven and leave to cool on the tray for 3 minutes, then transfer to a wire rack to cool completely.
Decorate the biscuit tops. Brush 12 of the cooled biscuits with the melted white chocolate, diagonally across half of the biscuit. Sprinkle the brushed chocolate evenly with pistachios and freeze-dried raspberries. Set aside.
Pipe small buttercream ‘kisses’ around the outside edge of the remaining 12 biscuits. Then, pipe jam into the centre of each buttercream edge. Top with the 12 decorated biscuits, pressing down very gently to sandwich.