In a medium bowl, combine flour, cocoa powder, baking soda and salt. Whisk together until ingredients are evenly distributed. Set aside for later.
1 Cup All-purpose flour, ⅔ Cup Unsweetened cocoa powder, Dutch-processed, 1 teaspoon Baking soda, ¼ teaspoon Sea salt
Using a stand mixer with the paddle attachment, mix the butter, granulated sugar and brown sugar on medium speed until the mixture becomes light and fluffy, about 2 to 3 minutes. Be sure to scrape down the sides of the bowl as needed. Note: A hand mixer can also be used for this step.
⅓ Cup Granulated sugar, ½ Cup Brown sugar, ½ Cup Unsalted butter
Add the egg and vanilla extract to mixing bowl. Mix on medium speed until combined, scraping down sides of bowl as needed.
1 Large Egg, 1 teaspoon Vanilla extract
Add flour mixture and mix on low speed until combined.
Add the milk and mix just until everything comes together. Be careful not to overmix, or the cookies can turn out dense and tough.
2 teaspoons Whole milk
Add chocolate chips to bowl and mix briefly until evenly distributed.
¾ Cup Mini-chocolate chips
Cover cookie dough with plastic wrap and place in refrigerator for at least 4 hours. (note - the cookie dough may be a bit sticky at this point; it will firm up while chilling in the refrigerator).