In a bowl, beat the butter, sugars and golden syrup until pale and fluffy, add the orange zest, scrape down the sides of the bowl and continue to beat until mixed. Add the egg and stir to combine.
Mix all the dry ingredients, tip into the butter mixture, stir, then add the chocolate and pecans, and stir again.
Place in a container and chill for two to four hours. Shape into 60g balls, then chill overnight.
Heat the oven to 180C (160C fan )/350F/gas 4. Before baking, dip the balls of dough into a bowl of demerara sugar. Bake on a tray lined with greaseproof paper for 12-14 minutes, then remove and leave to cool on the tray before storing or wrapping.