1. Preheat oven to 375 degrees F. Line a baking sheet with parchment paper or silicone mat. Set aside.
2. In a medium bowl, whisk together the flour, baking soda, salt, and cocoa powder. Set aside.
3. With a mixer on medium speed, cream the butter and sugars together until smooth. Add the eggs, one at a time. Next, add in vanilla extract. Mix until blended well, scraping the sides of the bowl as needed.
4. Slowly add the flour mixture and mix just until the flour disappears. Stir in the chocolate and Oreos. Drop cookie dough by scant ¼ cups onto the baking sheet.
5. Bake cookies for 8-10 minutes. Don't over bake - if the cookies are set around the outside but still soft in the middle, they're ready to come out. Remove from the oven and let sit on baking sheet for 3-5 minutes. Move to a cooling rack and cool completely.