Preheat the oven to 170°C/340F.
Cream together the softened butter, sugar, salt, vanilla extract, and golden syrup until combined.
Then add the room temperature eggs and mix through until light and fluffy.
Sift in the flour, baking powder, cocoa powder, and cornstarch. Add in the coconut and mix until just combined.
Place the biscuit dough onto a sheet of cling film or plastic wrap and bring it together into a disc or rectangle, seal tightly and place in the fridge for 30 minutes to 1 hour.
Place the dough on a clean working surface, flour the top of the dough, and roll out until about 0.5cm thick.
Cut out rounds or squares about 4-5cm big. Place these rounds back in the fridge for another 30 minutes.
Place the biscuits on a baking tray lined with baking paper about 3cm apart. Bake for 10 to 12 minutes. Allow cooling on the baking tray for 5 minutes before transferring to a wire cooling rack.
Melt the chocolate by zapping the chocolate in the microwave at 20-second intervals, stirring well between each interval. Otherwise, place the chocolate in a glass dish over a saucepan of water and melt over low-medium heat.
Sandwich the biscuits together and allow to set before serving.