"These pancakes are a chocolate chip cookie pancake and a brownie in one! As an added bonus, you have a pan of brownies to nosh on later! Breakfast and midnight snack in one recipe. Serve pancakes immediately, perhaps with a dollop of whipped cream!"
Preheat oven to 350 degrees F (175 degrees C). Line a 9-inch baking pan with parchment paper; grease parchment paper with cooking spray.
Whisk flour, sugar, baking powder, baking soda, and salt together in a bowl.
Combine buttermilk, egg, butter, and vanilla extract together in a small bowl, beating to break up the egg. Add flour mixture; stir until just combined. Fold chocolate chips gently into the batter. Allow batter to rest for 5 minutes.
Combine brownie mix, oil, eggs, and water in a large bowl; whisk together until smooth.
Pour 1/2 cup of the brownie batter into a squeeze bottle, pastry bag with a small round tip, or large resealable plastic bag with corner snipped off. Reserve remaining batter.
Heat a large nonstick skillet over medium-low heat. Drop 1/3 cup pancake batter into the skillet, shaking skillet to spread batter evenly. Drop 5 nickel-size dollops of brownie batter over the pancake; swirl using a skewer or knife edge. Cook until edges are dry, 2 to 3 minutes. Flip and cook until set on the other side, 1 to 2 minutes. Repeat with remaining batters.
Pour reserved brownie batter into the prepared pan.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 28 to 30 minutes. Cool on a wire rack before slicing.