Easy Chocolate Chip Brookies (Brownies + Cookies)

For the Brownies:
2 Follow recipe instructions on the back of the box. Mine called for 1 egg, 1/3 cup water, 1/3 cup oil. I always add vanilla extract and substitute some or all of the water with strong coffee or espresso to bring out the chocolate flavor.
For the Cookies:
5 In a large mixing bowl, beat butter & sugar with a hand mixer until smooth & incorporated. Add in the eggs & vanilla extract & mix until combined.
6 Add in the flour, salt, & baking soda. Mix until everything is well combined.
7 Sprinkle in the chocolate chips. Using a spatula, mix in the chocolate chips. The batter should be thick and sticky.
For the Brookies:
10 Preheat oven to 325F degrees.
11 Grease a 9x9 baking pan with oil and line with parchment paper.
12 Press the chocolate chip cookie mixture into the bottom to create a layer. If using, add the oreos on top in a single layer or skip this step.
13 Pour the prepared brownie mixture over that and bring to the edges.
14 Bake for 45-55 minutes. Make sure not to overbake. It's okay if the brownies feel slightly underdone in the middle. They will harden more as they cool!
15 Let cool completely! If you're adding peanut butter cups, cut them in half and layer on top of the cooled brownies with a sprinkle of sprinkles. Enjoy!