Soften the butter by weighing it out and then either briefly microwaving it or leaving it out on the worktop for an hour or two. Then weigh out the rest of the ingredients (except for the dark chocolate) into a large mixing bowl and put in the butter.
Using a wooden spoon or electric mixer with the paddle attachment, mix the ingredients to a paste and then stop. You don’t want to add too much air.
For the classic look of the biscuit place the paste into a piping bag with a star nozzle and pipe the mixture out onto non stick baking parchment or, if you have one, which we highly recommend, a mat like this.
Pipe the biscuits on the tray they will be baked on and make sure they are spaced sufficiently apart because they do expand.
Bake the biscuits at 170°c for 15 minutes until lightly golden brown. Then place them onto a wire rack to cool to room temperature.
Melt the chocolate and dip one half of the cooled biscuit into it to coat. Gentle shake off some of the excess chocolate and place the biscuit back onto the non stick mat or lightly greased baking parchment.
Leave the chocolate to set completely to avoid mess.