Preheat oven according to directions on brownie mix.
Prepare brownie mix according to package directions and set aside.
In a medium sized bowl, beat the cream cheese for a couple of minutes until smooth and creamy.
Add in the egg, flour, sugar and vanilla and stir mixture till combined.
Pour all but about 1/2 cup of the brownie batter into a prepared 9x13 pan.
Spoon the cream cheese mixture on top of the brownie batter.
Spoon the remaining brownie batter onto the top of the cream cheese mixture.
Using a knife, swirl the cream cheese and brownie batter together, creating a marbled effect.
Place in preheated oven and bake for 35-40 minutes, or until a toothpick inserted near the middle comes out mostly clean.
Remove from oven and allow to cool completely before cutting into pieces.