Mix the dry ingredients in a bowl and add the butter. Knead all the ingredients together into a smooth dough. Cover the dough tightly with plastic wrap and refrigerate for an hour.

Heat oven (190 °C /375 °F) and line 2 baking sheets with parchment paper.

Divide the dough into 4 balls. Roll each ball on a clean surface into a rope of 1 cm thickness in diameter. With a knife cut 5 cm long bars. Arrange the bars on the baking sheets and bake for about 15-20 minutes depending on your oven. Make a check after 10-12 minutes by turning one cookie to see the bottom. Be careful, cookies are soft and might break. When the bottom is darker than the chocolate colour, baking time is over even if the top of the cookie feels a little soft.

Cool 5 minutes on the sheet and then transfer onto a wire rack to cool completely.

Melt the chocolate in a Bain Marie and dip one end of each bar in the melted chocolate. Transfer onto a wire rack to dry. Keep well in an airtight container.