In the bowl of a stand mixer fitted with the paddle attachment, mix butter, brown sugar, and granulated sugar until light and creamy, about 3 minutes.
Add the eggs and vanilla and beat until just combined.
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.
Add the flour mixture to the butter mixture in three parts, pulsing the mixer to prevent the flour from flying out and mixing until just combined.
Using a wooden spoon or rubber spatula, fold in the chocolate chips, pecans, and chopped chocolate. The dough will be thick. If necessary, use your hands to combine.
Cover the dough with plastic wrap and refrigerate for 24-72 hours.
Preheat the oven to 375ºF. Line a baking sheet with parchment paper or a Silpat.
Using a kitchen scale, measure out 6 ounce balls of dough, using your hands to press them together and round them out. If you don’t have a kitchen scale, just divide your dough evenly into seven balls.
Place the dough balls on the prepared baking sheet, working in batches as necessary to prevent them from spreading into each other. I was able to fit four cookies per sheet.
Using the palm of your hand, flatten the dough slightly. It should still sit up pretty high, but you just want to take the dome of it down a little bit.
If desired, press extra chocolate chips and pecans into the top of the dough. You can also sprinkle with flaky sea salt if desired.
Bake the cookies for 16-17 minutes or until the edges are set and the middle looks soft but not glossy.
Allow the cookies to rest on the baking sheet for 5 minutes before transferring to a cooling rack to cool completely.
Notes
Tips for customizing bakery style double chocolate chip cookies
Omit the pecans for a nut free treat
Swap the pecans for walnuts or macadamia nuts
Use a mix of chocolate chips such as white chocolate, semi-sweet, and dark
For a smaller cookie, use 3 ounces of dough and bake for 11 minutes
If you choose not to chill the dough, cut the baking time down by a few minutes