Preheat oven to 350 degrees F.
Line a cookie sheet with parchment or a silicone baking mat, and set aside.
Using a stand mixer with a paddle attachment, beat butter and sugar together until it is light and fluffy. The butter should be soft when you start, and after beating it together, it will be lighter in color.
Meanwhile, in a large bowl, whisk together the flour, cocoa powder, baking soda, and salt.
To the butter mixture, add eggs, one at a time, while continuing to mix. And the vanilla extract.
Once mixed together, combine slowly, adding the flour mixture to the butter mixture a little at a time, making sure you don't overmix, or it will make the cookies tough.
Using a large cookie scoop (3 Tbs), scoop out dough, and place 2-3 inches apart on prepared cookie sheet (I put 6 on each sheet, makes 18-20 cookies)
Bake 10-12 minutes, until no longer gooey in the center.
Remove from oven, let sit on the pan for 1 minute, then transfer to a cooling rack.