Ingredients:
- ½ cupunsalted butter, softened
- ½ cupgranulated sugar
- ½ cuppacked light or dark brown sugar
- 1large egg, room temperature
- 1 tsppure vanilla extract
- 1 cupall-purpose flour, spooned and leveled
- ⅔ cupnatural unsweetened cocoa powder (not Dutch-process)
- 1 tspbaking soda
- ⅛ tspsalt
- 1 tbspmilk, any kind
- 1¼ cupssemi-sweet chocolate chips
- a few extra chocolate chips, for the tops (optional)
Steps:
Beat the , and on medium-high for about 3 minutes, until light and fluffy. Beat in the and , scraping the bowl as needed.
Whisk the , , and in another bowl. Add to the wet ingredients on low and mix until combined. The dough will be thick.
On high, beat in the , then the . The dough will be sticky.
Cover tightly and chill at least 3 hours, up to 3 days. Overnight is best, and colder dough makes thicker cookies.
Let the dough sit out 10 minutes (about 20 if chilled longer than 3 hours) so it's easier to scoop.
Heat the oven to 350°F and line baking sheets with parchment or silicone mats.
Scoop heaping 1½ tablespoon (35 to 40 g) balls and roll them taller than they are wide. Space them 2 to 3 inches apart.
Bake 11 to 12 minutes, until the edges look set and the centers still look soft. If they haven't spread by minute 9, bang the pan on the counter 2 or 3 times and keep baking.
Cool 5 minutes on the sheet. Press a few into the warm tops if you like, then move to a rack. They flatten a little as they cool.