These delicious homemade versions of the favourite British biscuit have a creamy milk chocolate ganache filling. Prue’s top tip is to be accurate with rolling and cutting the dough, in order to get 16 biscuits which are all the same shape and size.
For the biscuit dough, sieve the flour, cocoa powder and salt together into a bowl.
In the bowl of a stand mixer, fitted with the paddle attachment, cream the butter and sugar together until creamy, but not too light or aerated.
Add the sieved dry ingredients and the egg and mix on low until just combined. Do not over mix.
Line a baking sheet with baking paper and scrape the dough into the middle of the paper. Cover the dough with another sheet of baking paper, then using a rolling pin, roll the dough out to the thickness of a £1 coin. Place in the freezer for 15 minutes to firm up.
For the chocolate ganache filling, tip the chocolate into a small heatproof bowl. Pour the cream into a small pan and heat to just below boiling point. Pour the hot cream over the chocolate and leave to stand for 4 minutes, then stir until the chocolate has melted and you have a smooth ganache. Leave to cool, then chill until set to a piping consistency.
Remove the dough from the freezer and slide off the baking sheet. Peel the top piece of paper off the dough. Using a ruler, cut 16 rectangles out of the biscuit dough, each measuring 8cm x 3cm, then place them on a baking sheet lined with baking paper.
Working quickly before the dough softens, use the stamp provided to stamp SU2C in the centre of 8 of the dough rectangles. Using a cocktail stick or skewer, prick 7 small holes along the long, top and bottom edges of the 8 stamped biscuits.
Place in the freezer to chill for 10 minutes, then bake for 10-12 minutes at 180°C/160°C fan/350°F/Gas 4. Remove from the oven and leave to cool on the baking sheet to firm up, then transfer to a wire rack and leave to cool completely.
Spoon the chocolate ganache into a piping bag fitted with a ½cm plain nozzle.
Turn the 8 non-stamped biscuits upside down and pipe the chocolate ganache over them, then sandwich with the 8 stamped biscuits.