- 1 cup butter, softened
- 3/4 cup brown sugar
- 1/2 cup white sugar
- 1 egg
- 1 teaspoon vanilla extract
- 2 1/4 cups all-purpose flour
- 1/2 teaspoon salt
- 1 teaspoon baking soda
- 1 (20 ounce) package brownie mix (such as Hershey® Triple Chocolate Chunk)
- 2 tablespoons milk
- 1 tablespoon water
- 1 1/2 teaspoons vegetable oil
- Preheat oven to 350 degrees F (175 degrees C).
- Beat butter, brown sugar, and white sugar together with an electric mixer in a large bowl until smooth. Add egg and vanilla extract and beat until smooth.
- Mix flour, salt, and baking soda together in a separate bowl; add to butter mixture and blend until just incorporated into a dough.
- Beat brownie mix, milk, water, and vegetable oil together in a separate bowl; add to dough and stir gently to keep the two batters distinct but somewhat evenly mixed.
- Drop dough onto ungreased baking sheets by heaping tablespoonful.
- Bake in preheated oven until set in the middle and crackling on top, 10 to 12 minutes. Cool cookies on sheets for 5 minutes before moving to a wire rack to cool completely.