Preheat oven to 375F and line a baking sheet with parchment paper.
Mix butter, brown sugar and sugar together with an electric mixer until smooth. Add egg yolk and vanilla extract to the bowl and mix again.
Add all purpose flour, baking soda, baking powder and salt to the mixing bowl and mix again with the electric mixer. It will seem too crumbly at first, but keep mixing until the dough comes together.
Pour chocolate chips into the bowl and mix in with a flat spatula.
Scoop out about 3 tbsp of batter per cookie and roll into a ball. You should have 6 cookie dough balls. Place them on the lined baking sheet with space between each cookie.
Bake at 375F for 11 minutes. Remove from oven and top with flakey sea salt. Allow to cool and enjoy!
Notes
Only use egg yolk - using a whole egg will not work
Substitute all purpose flour with gluten free all purpose flour blend to make these cookies gluten free