In a large bowl, combine butter and sugars. Beat on low with an electric hand mixer or in the bowl of a stand mixer until smooth and creamy. Add the egg and vanilla. Mix on low until combined. Set aside.
1 1/2 cups butter, 1/2 cup white granulated sugar, 1/2 cup brown sugar, 1 large egg, 1 teaspoon vanilla extract
In a separate large bowl, combine dry ingredients. Whisk to combine and gradually add (in batches) to wet ingredients. Beat on low until combined, and then continue with the next batch. Mix until ingredients are almost combined; a few lumps here and there are fine.
1 1/2 cups all purpose flour, 1 teaspoon baking soda, 1/2 teaspoon salt, 3/4 cup cocoa powder
Stir in the chocolate chips. The batter will be sticky. Freeze the batter for 15-30 minutes to an hour or at least 1 hour in the fridge. The batter should resemble playdough after freezing/chilling.
3/4 cup semisweet or milk chocolate chips
Scoop 2- 2 ½ tablespoonfuls of batter, rolling it into about 2 inch balls.
Arrange the cookie balls on a baking sheet lined with parchment paper at least 2 inches apart. Don’t press down!
Bake for 10-12 minutes (the time varies due to different ovens). I like to add chocolate chips on top after baking for decoration purposes, but this is optional. After baking, the cookies will have a soft center inside. Once they cool down they will set and the texture inside remains soft, chewy, and buttery.
Let the cookies stay on the pan for 5-10 minutes before transferring to a wire rack.
Notes
It is important to chill the batter between the batches if you can't bake the cookies all at the same time.