Preheat the oven to 180°c and line a baking sheet with baking paper.
Using an electric mixer on a medium speed, beat butter sugars and vanilla for 1 minute until pale.
Add the egg and mix for a further 30 seconds.
Add flour and salt. Mix for 1 minute (you might need to use the dough hooks on your mixer for this step)
Add chocolate chips and mix through with a spoon.
Roll tablespoon sized balls and place them on a baking tray leaving a gap for them to spread.
Flatten each ball slightly.
Bake for 10 – 12 minutes and remove from the oven to cool.