Preheat oven to 350℉ (unless otherwise stated on your box) and grease a 9x13 pan. Mix the brownie mix and ingredients on box according to the package directions. If your mix doesn’t include a pouch of chocolate syrup, you can enhance the flavor by adding one heaping tablespoon of chocolate syrup. (I usually use Hershey's)Once combined, spread the batter evenly into the greased 9x13-inch pan.
In a bowl, beat the softened cream cheese until smooth, then mix in the egg, sugar, and vanilla until fully blended. Pour this cream cheese mixture over the brownie batter. Using a butter knife or spatula, gently swirl the two layers together to create a marbled effect. It may be necessary to gently lift some of the brownie batter up to the cream cheese layer in order to get a swirl. Afterward, sprinkle chocolate chips evenly on top and bake according to the brownie mix instructions. Keep in mind it may take a minute or two longer than the box suggests. The brownies are ready when a toothpick inserted in the center comes out clean or with just a few moist crumbs. Allow the brownies to cool for about an hour before cutting into squares and serving.