In a microwavable mug mix the butter and sugars together.
Add egg yolk and vanilla and continue mixing .
Stir in flour, salt and chocolate chips, then mix until all ingredients are fully combined.
Microwave for 40-60 seconds (check after 40 seconds to check if it is done, you might have to play around with the timing as all microwaves are different)
IMPORTANT NOTE:My microwave is 1200 Watts and my cookie took 40-45 seconds. Don’t over cook or they can dry out. Mug cookies are best eaten while still warm
Try topping your creation with whipped cream or vanilla ice cream and chocolate sauce