Preheat the oven to 350 degrees F and line a baking sheet with a silicon baking mat or parchment paper.
Using a hand or stand mixer, cream together the butter and sugars on medium low speed until light and fluffy. This will take 1-2 minutes.
Add the egg and vanilla. Beat until well combined, about 1 minute.
In a separate bowl, sift together the all-purpose flour, cocoa powder, and baking soda. Whisk to combine.
Add half of the dry ingredients to the wet mixture. Mix on low until combined, then slowly add remaining dry ingredients to the cookie dough. Be careful not to overmix.
Pour in the chocolate chips. Use a spatula or large wooden spoon to fold the chocolate chips into the cookie dough.
Scoop twelve 1 and ½ tablespoon sized cookie dough balls out onto the parchment paper lined baking sheet. Place 3 inches apart. They should be about the size of a ping pong ball.
Bake at 350F for 10-11 minutes on the middle oven rack, until the edges appear crisp. They will look underdone when removed from the oven. Let rest at least 5 minutes before transferring to a cooling rack.
Sprinkle cookie tops with flaked sea salt before they cool. Enjoy!
Notes
Cocoa powder: An equal amount of Dutch process cocoa powder can be used for richer cookies.
Flaked salt: If you don't have flaked salt you can add ⅛ teaspoon table salt to the cookie dough.
Storage: Keep cookies in an airtight container at room temp for up to 4 days. To keep the cookie soft, place a slice of bread in the container.
Freezing instructions: Let cookies cool entirely before transferring to an airtight container. Freeze for up 3 months. They will thaw quickly at room temperature. to freeze the cookie dough, roll into individual balls or freeze an entire batch together. Let the cookie dough thaw overnight in the fridge before using. Individual cookie dough balls can be baked immediately, just add an extra minute in the oven.
Spoon and level flour: This is the most consistent way to measure flour. Use a spoon to scoop flour into the measuring cup. Wipe off excess flour with the back of a knife. Don't pat the flour down or shake the measuring cup.