In a small saucepan combine the butter and chocolate chips. Heat over medium heat until melted, stirring frequently. Once melted remove from the heat and set aside.
In the bowl of a stand mixer fitted with a paddle attachment combine the eggs, sugars, vanilla, and salt. Beat until combined, 3-4 minutes. With the mixer on low, slowly pour in the melted chocolate mixture. Mix to combine, scrape down the sides.
Sift in the flour, baking soda, and cocoa powder, mix on low until fully incorporated. Cover and chill for 30 minutes.
Preheat oven to 350 degrees F and grease or line a cookie sheet. Using a 1 oz. cookie scoop or a measuring spoon, scoop dough out onto the prepared cookie sheet.* Spread about 2 inches apart.
Bake at 350 for 9-10 minutes. Remove from the oven and sprinkle with flaky salt, the cookies will be very soft and gooey when they come out of the oven, . Allow to set for 5-10 minutes before transferring to a cooling rack to finish cooling.
Notes
*The cookie dough will be very sticky, greasing your hands and/or the cookie scoop can help with any sticking.