Preheat the oven to 160°C.

Melt butter in a saucepan over medium heat (or in the microwavand set aside to cool slightly. Pour butter into a large bowl and stir in brown sugar and caster sugar until smooth and sugar is mostly dissolved.

Lightly beat the egg with a whisk or fork and stir into the sugar mixture along with the vanilla.

Sift flours and baking powder together into a small bowl and then gradually mix into sugar mixture until combined. Stir in chocolate chips.

Drop rounded tablespoons of the cookie mixture onto lined baking trays. Then bake for 10-12 minutes or until golden.  Then remove from oven and allow to cool on trays for 3 minutes before transferring to a wire rack to cool completely.