Preheat the oven to 350 F. Line 2 baking sheets with parchment paper.
Microwave the butter in a microwave safe bowl until almost melted. Whisk the butter adding the sugars; mix until well-combined. Stir in vanilla and egg until incorporated. Add the flour, cocoa powder, baking soda, and salt. Mix dough until just combined. And no streaks. Dough should be soft and a little sticky. Stir in chocolate chips and pieces. Scoop out 1 ½ tablespoons of dough (medium cookie scoop) and place 2 inches apart on baking sheet. Bake for 7-10 minutes, or until cookies are set. They will be puffy and still look a little underbaked in the middle.
Notes
Using a high milk fat yields a more chocolate flavor cookie -slightly underbaking will make a chewier cookie -if using table salt only use ¼ teaspoon.