Preheat the oven to 350°F. Line baking sheets with parchment paper or silicone mats and set aside.
Using a large bowl and an electric mixer, beat the butter and both sugars together on medium-high speed until they are light and fluffy.
3/4 cup butter, 3/4 cup granulated sugar, 3/4 cup brown sugar
Add the eggs and vanilla. Beat again for 2-3 minutes, until fully combined, scraping down the sides of the bowl at least once to ensure everything is evenly mixed.
2 large eggs, 2 teaspoons vanilla extract
Sprinkle the flour, cocoa powder, baking soda, and salt over the mixture. Mix on low speed just until evenly combined.
2 cups all-purpose flour, 2/3 cup unsweetened natural cocoa powder, 1 teaspoon baking soda, 3/4 teaspoon flaked sea salt
Scoop the dough out into heaping Tablespoons onto the prepared sheet pan. (A #40 cookie scoop works well.) Roll into smooth balls if you like. Bake for 9-11 minutes, until the tops are fully set and the edges are slightly crisp. If you want to add extra sea salt, sprinkle it on immediately after the cookies come out of the oven.
Allow to cool on the sheets for about 10 minutes before removing to wire racks to cool completely. Enjoy!