You will need 250g unsalted butter, 55g icing sugar, 225g plain flour, 75g corn flour and 300g dark chocolate. Soften the butter by weighing it out and leave it out on the worktop for an hour. Weigh out the rest of the ingredients into a mixing bowl and put in butter. Mix the ingredient to a paste and then place it into a piping bag that has star nozzle. Bake the biscuit at 170 °C until golden brown and finally melt the chocolate and dip the cooled biscuits into it to coat.