Preheat oven to 350°. Line a cookie sheet with silicone or parchment paper, or spray with cooking spray
In a large bowl, beat together the soft butter, brown sugar, and white sugar with an electric mixer for 2-3 minutes, or until fluffy.
Add the cocoa powder, dry pudding mix, eggs, and vanilla. Beat until combined.
Add the flour, salt, baking soda, and cornstarch. Stir until just combined, then stir in the chocolate chips. (I like to reserve some for the tops of the cookies.)
Scoop dough by tablespoonfuls, and roll into balls. Mine weighed about an ounce each.
Place cookie dough balls on the pan, at least 2 inches apart.
Bake in a preheated oven at 350 degrees for about 10 minutes. Immediately press a few chocolate chips into the top of each cookie.