Method

• 1.
  Place the butter, caster sugar, flour and vanilla in the bowl of a stand mixer fitted with the paddle attachment and beat on low speed for 1-2 minutes until the mixture forms a fine crumb. Add chocolate and Werther’s Originals and beat until well combined. Shape dough into a 25cm x 5cm square log, wrap in plastic wrap and chill for 2 hours, or up to 4 days.

• 2.
  Preheat oven to 180°C. Line 2 baking trays with baking paper.
• 3.
  Scatter demerara sugar on a tray. Unwrap chilled dough, brush 1 side with egg white and press onto sugar. Repeat on all sides, until the log is completely coated in sugar. Chill for a further 15 minutes to allow sugar to stick to the dough. Slice dough into 1cm-thick pieces. Arrange 3cm apart on prepared trays and bake for 15-20 minutes until golden. Cool completely before serving. Cookies can be stored in an airtight container for up to 1 week.