Preheat oven at 200°C and grease baking trays lightly with melted butter.
Cream butter with both types of sugars, essence and molasses until fluffy. Beat in the egg, then add milk and sifted dry ingredients to mix. Halfway through, add chocolate chips. Continue to mix until well combined.
Roll dough into a long cylinder with a diameter of 3-5cm. Wrap up with cling film and chill for 5-6 hours or until firm. Cut dough into 0.5cm thick slices.
Arrange dough pieces on prepared baking trays and bake for 10-12 minutes or until firm to the touch.
Leave the cookies in the trays for 5-6 minutes before removing them and placing them onto wire racks to cool completely.