Next, prepare your brownie mix according to the package directions. Add the prepared brownie batter to your lightly greased baking pan. (I used a heart-shaped pan here, but a 13x9-inch pan would work just as well.
In a large bowl, beat together the cream cheese, sugar, egg, and vanilla extract until smooth. Add spoonfuls of the cream cheese mixture to the top of your brownie batter. Use a wooden skewer or toothpick to swirl the cream cheese mixture into the batter.
Bake according to the package directions, adding an extra 4-5 minutes to compensate for the cream cheese layer.
Remove from the oven and allow to cool for 5-10 minutes before removing from the pan. Top with sprinkles for added color and fun.
Notes
*Amount will vary based on your particular brownie mix.