Preheat the oven to 190ºC/170ºC Fan and Line 2 Large baking trays with parchment paper.
Melt the butter slowly until it is fully melted, leave to cool for a couple of minutes.
Once cooled, beat in both the light brown soft sugar and granulated sugar until they are all thoroughly combined.
Add the egg, egg yolk and vanilla extract and beat the mixture until the mixture becomes much lighter in colour, is smooth, and has increased in volume.
Add the dry ingredients (plain flour, bicarbonate of soda, and sea salt) and beat again until smooth.
Fold through the chocolate chips.
Using a 5cm Scoop, portion the cookies onto the trays (I did 6 per tray).
Bake the cookies in the oven for 12-13 minutes for softer chewy cookies, OR 15 minutes for soft/crunchy cookies.
Leave the cookies on the tray for 5 minutes after they have finished baking, and then transfer to a wire rack and continue to cool! Enjoy!
Notes
These cookies will last for 4-5+ days at room temperature
These cookies will freeze for 3+ months
The cookie dough will also freeze raw for 3+ months, add 1-2 mins to the baking time