Stir all the dry ingredients together in a bowl or a food processor. Add the butter and chilli and rub in with your fingertips or process until the mixture resembles fine breadcrumbs.
Add the syrup then mix together first with a spoon then squeeze the crumbs together with your hands to form a ball.
Knead in the chopped chocolate then shape the dough into a log and slice into 12. Roll each piece into a ball and arrange on 2 large greased baking sheets. Cook one baking sheet at a time in the centre of a preheated oven, 180°C (350°F), Gas Mark 4, for 8–10 minutes until browned and the tops are craggy.
Leave to cool for 1–2 minutes then loosen and transfer to a wire rack. These cookies are best eaten on the day they are made and delicious served while still warm.