Whisk together the softened butter, brown sugar and white sugar until light and fluffy.
Add in the egg, vanilla extract and salt and mix until combined.
Sift in the plain flour and add in the chocolate chips. Mix all together until fully combined.
Once you have a smooth cookie dough, press it into an 8x8 baking tin lined with baking paper. Refrigerate for at least 30 mins before baking.
Bake in a pre-heated oven at 180℃ for 25 minutes. The cookie will be brown around the edges and will still be soft in the centre.
Remove from the oven and allow it to completely cool before slicing.
