Preheat the oven to 180 C (360 F). Line two baking trays with baking paper. In a large mixing bowl, add the butter and sugars and beat using an electric beater for a minute or two until smooth and creamy. Add the egg and the vanilla and beat until combined, scrapping down the sides. Then add the molasses. Add the sifted flour, baking soda, ginger and cinnamon and stir using a wooden spoon.
Roughly chop the chocolate into a mix of large and small pieces. Then add the chocolate chunks into the cookie dough. Cover with plastic wrap and place in the fridge for at least 30 minutes. Roll teaspoons of the mixture into balls, roll them in a little extra brown sugar and then place on the prepared baking trays, leaving room for the cookies to flatten out. Place in oven for 10 minutes or until golden brown on the edges. Leave to cool for 5-10 minutes before transferring to a wire rack to cool completely.