Preheat your oven to what the directions state on the box of brownies you're using. Ghiradelli says to preheat to 325F.
In a large bowl, mix together your brownie mix, eggs, milk (not water!), oil, and vanilla.
Spray a 9x11 sheet pan with cooking spray.
Pour batter into a prepared 9x11 sheet pan.
Bake for 35-40 minutes, or until a toothpick comes out clean.
Once your brownies are done, allow them to cool.
While they are cooling make your cream cheese frosting.
Using either a stand mixer or a hand mixer, beat together your cream cheese and butter over medium speed.
Slowly add in the powdered sugar.
Lastly, add in the vanilla extract and whip until fluffy.
Spread on your cooled brownies, slice and enjoy!