Microwave butter and chocolate chips in microwave-safe bowl until melted; heat in 30 second intervals, stirring in between. Allow to cool for 5 minutes.
In the bowl of a stand mixer using the paddle attachment, beat the eggs, vanilla, and sugar together on medium speed for 3-4 minutes, until creamy.
Meanwhile, in a medium size bowl, stir together flour, cocoa powder, baking powder, and salt.
Once butter-chocolate mix has cooled slightly, add to ingredients in stand mixer, mixing just until combined.
Gradually incorporate dry ingredients into the wet ingredients, beating on low speed and scraping down the sides as needed. Mix until just incorporated. The dough will seem very liquid-y and more like batter than dough, but it will stiffen in the fridge.
Chill dough in fridge for at least 1 hour or overnight. You don't want to skip this step, as the chilling time stiffens the dough!
Once chilled, preheat oven to 350 degrees.
Scoop rounded tablespoonfuls of cookie dough onto parchment or silicone-lined baking sheet, about 2 inches apart. Bake for 10-12 minutes.
Let cookies sit on baking sheet for about 10 minutes before transferring to a cooling rack.