Preheat your oven according to the box instructions. Line a 9×9 baking pan with tinfoil so that it overhangs on two sides and spray with cooking spray.
In a large mixing bowl, prepare the brownie batter also according to the box instructions.
Add in the raspberry extract and beat well to combine. Fold in the raspberries, taking care not to mash them all up.
Pour the batter into the prepared pan, and sprinkle with the dark chocolate chips.
Bake per the box instructions. Remove from the oven and let set 15 minutes. Then carefully lift the brownies using the tinfoil. Place the brownies (still on the tinfoil) onto a cooling rack until the brownies are no longer warm.
Remove the tinfoil and transfer the brownies to a cutting board. Cut into squares and serve with a scoop of ice cream or whipped cream for a truly decadent treat.
Store leftovers in the refrigerator.