Preheat your oven to 350 degrees Fahrenheit, and line rimmed baking sheets with parchment paper. Set aside.
In a large bowl, whisk together the flour, cocoa powder, salt, and baking soda. (Please see notes in the post about measuring flour.)
Using a stand mixer or a large bowl and a hand mixer, beat together the room temperature butter, granulated sugar, and brown sugar. Beat until light and fluffy, about 3 to 6 minutes.
Beat in the peanut butter, scraping down the sides as you go, until fully incorporated.
Beat in the eggs, one at a time, and then beat in the vanilla extract.
Add in the flour mixture. Beat on low until combined enough that it won't beat out of the bowl. Turn the beater up high and beat just long enough that the flour mixture is fully incorporated.
Using a 1 1/2 tablespoon cookie scoop, form into balls. Drop onto the prepared sheet, placing each cookie 2 inches apart. Press down with a fork, first one way, than the other to make a hash mark.
Bake for 8 to 10 minutes, rotating the pan half way through baking. (I like my cookies on the almost underdone side, so what you see pictured was baked for 8 minutes.) Allow to cool for 5 minutes on the tray before transferring to a cooling rack. Once completely cooled, store in an airtight container for up to 1 week.