Preheat the oven to 350 F, and position a rack in the center of the oven. Line two large baking sheets (15x20 inches) with parchment paper.
In a saucepan, combine the chocolate chips and butter. Melt the chocolate and butter over medium low heat, stirring frequently, until smooth. Remove from the heat.
In the bowl of your stand mixer fitted with the whisk attachment (or using a hand held electric mixer), beat the eggs and sugar on medium speed for several minutes until pale, foamy, increased in volume and thick with a "ribbony" texture.
Add the melted chocolate and butter to the egg mixture and whisk until combined.
Add the sifted cocoa powder, vanilla and salt, and whisk until combined. The batter will be fairly thin, like brownie batter, not thick like cookie dough.
Set the bowl of batter in the refrigerator to chill and slightly thicken for just 10 minutes.
Use a medium cookie scoop with a release lever (with a 2 tbsp capacity) to scoop the batter into dollops on the prepared baking sheets. Leave 3-4 inches between each, so the cookies have room to spread.
Bake one pan of cookies (with the other pan resting at room temperature) for about 10-11 minutes, until the cookies have spread and the tops crackled. Immediately after taking the pan out of the oven, use a round cookie cutter to "scoot" it around the cookies, pulling the edges in for perfectly circular cookies.
Cool the cookies on the pan for 10-15 minutes until set, then gently transfer them to a cooling rack to cool completely. As the cookies cool, they will settle and flatten so the cooled cookies are fairly thin.