Preheat the oven to 350°F. Line a baking sheet with a silicone baking mat or parchment paper.

In a medium bowl, whisk together flour, baking soda and salt and set aside.

In a large microwave-safe bowl, melt the butter (I like to do this in 15 second increments at 50% power, but you can also do it in a small saucepan on the stovetop and transfer it to a bowl afterward). While the butter is still warm, add the cocoa powder to the butter and whisk until very smooth. Whisk in sugar, vanilla extract and buttermilk.

Gradually add the flour mixture and stir until no streaks of flour remain (I like to stir in about ⅓ of the mixture at a time to fully, evenly incorporate it). Gently stir in the chocolate chips.

Drop dough by heaping tablespoons (I like using a #50 scoop) onto prepared baking sheet, leaving a few inches in between each cookie to allow for spread.

Bake for 10-14 minutes, until cookies are set around the edges.

Cool for 3-5 minutes on the baking sheet, then use a spatula to gently transfer them to a wire rack to cool completely.