Preheat the oven to 350° F. Allow the butter to soften for 20 minutes. Combine the butter with the brown and granulated sugar. Beat on medium speed until well combined, 2-3 minutes.
Next add the eggs, egg yolks and vanilla extract and continue beating until well incorporated.
Add the cocoa powder and beat until well combined.
In a separate bowl, combine the remaining dry ingredients: flour, salt and baking soda. Stir to combine and slowly add the dry ingredients into the dough, mixing on low speed until dough starts to form. As the dough thickens, add the chocolate chips. Beat until incorporated.
Line a baking sheet with parchment paper or use a silicone baking sheet. Using a large cookie scoop, place two scoops of the dough, one stacked on top of the other, and place on baking sheet, 2 inches apart. Sprinkle with flaky sea salt.
Bake for 15-16 minutes. The center of the cookies should be slightly under baked but not too gooey. Allow to cool on the baking sheet for 10 minutes before transferring to a wire rack to cool.
