Using a mixer, mix the butter, brown sugar, and granulated sugar until fluffy.
Add in vanilla and eggs, one at a time, and mix until light and smooth.
Mix in the cocoa powder.
In a separate bowl, sift the flour, baking soda, and salt, and add to the mixture until everything is combined. Add in a little bit of water if necessary.
Fold in the chocolate chips.
Form small dough balls and place them ~2 inches apart on a baking tray. Use your hands or a spoon to slightly flatten the dough.
Bake for 8-10 minutes at 350°. Cookies should look a bit undone — cool for 10 minutes outside the oven to let the cookies cook a bit more on their own.