Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper.

Cream together the butter, light brown sugar, and granulated sugar until light and fluffy.

Mix in the egg yolks and vanilla extract until pale and airy.

Gradually add in the flour, cocoa powder, salt, baking powder, and baking soda until just combined.

Fold in the chocolate chips until evenly distributed in the dough.

Scoop the dough into 18 balls and place on prepared baking sheets, spaced apart.

Bake for 10-12 minutes until edges are set and centers are slightly soft.

Sprinkle flaky sea salt on cookies after baking and let cool for 5 minutes on baking sheets.