200g butter, room temperature
120g castor sugar
260g plain flour
1/4 tsp fine salt
3 Tbs cocoa
granulated sugar / icing sugar to decorate (optional)
To make the butter biscuit dough: place 100g butter and 60g castor sugar in a bowl and cream until combined and fluffy. Add 150g flour and half the salt and mix until the dough comes together, scraping down the sides of the bowl as necessary. Continue to mix until you have a smooth dough, then set aside.
To make the chocolate biscuit dough: place the remaining 100g butter and 60g castor sugar in a bowl and cream together. Add the remaining 110g flour, salt and cocoa and mix to form a smooth dough.
Dust your work surface with plenty of flour. Roll the chocolate dough into a square (approximately 21cm) with a thickness of 5mm. Repeat with the butter biscuit dough. Place the chocolate square on a baking tray and paint the surface with a little water. Carefully lift the butter biscuit square and place on top of the chocolate layer. Press down gently. Cover the biscuit dough with plastic wrap and chill in the fridge for 15 minutes.
Preheat your oven to 170°C.
Line a baking tray with baking paper. Remove the biscuit dough from the fridge and trim the edges to give you a neat square. Cut the dough into squares roughly 4cm each and arrange on the baking tray. Use a fork to prick the top of each biscuit. (Optional: sprinkle granulated sugar over the cookies before baking for extra crunch.)
Bake the biscuits for 20 minutes until golden, turning the tray after 10 minutes for even baking. Transfer the biscuits to a cooling rack.
Serving suggestion: dust the biscuits with some icing sugar before serving. If you are feeling decadent you could also drizzle the biscuits with melted chocolate.