Preheat oven to 350 ℉. Prepare a 9x13 inch baking dish with baking spray or parchment paper. In a mixing bowl, combine the butter, white sugar, and brown sugar together and mix on medium/high speed using an electric mixer for about 3 minutes, scraping the sides of the bowl as necessary. It'll look whiter and should look slightly fluffy.
Add vanilla and both eggs, mixing well until eggs are mixed in well, for 1-2 minutes. Scrape the sides of the bowl as necessary.
Add in the flour, cocoa powder, baking soda, and salt and mix slowly until a dough forms and all of the flour pockets are gone, 1 minute or more.
Add in the chocolate chips last, save about ¼ cup or a handful to sprinkle over the top.
Spread into the prepared 9x13 inch pan, you can use a flat cup to help press it into the pan. Sprinkle with extra chocolate chips (optional).
Bake at 350 ℉ for 25-30 minutes. Dark pans for 25 min, and thick ceramic pans will take 28-30 minutes.
Cool for at least 20-30 minutes before slicing, it's much easier if they are cooled completely to room temperature. Enjoy!
Notes
Store at room temperature for up to 3 days. Freeze for up to 2 months.