Preheat the oven to 350°F.
Line an 8 x 8 or 9 x 9 baking dish with parchment paper. Use the butter wrappers to grease the parchment paper. Set aside.
To a bowl add the butter and sugars. Mix with a stand mixer or hand mixer over medium speed for 2 minutes.
Add the eggs and vanilla to the bowl. Mix with the stand mixer or hand mixer until combined. Set aside.
In a separate bowl add the rest of the bars' ingredients. Mix with a whisk or fork until combined.
Transfer the flour mixture to the wet ingredients. Use a spoon to mix just until combined. Do not overmix.
Transfer the bar mixture to the baking dish.
Bake for 25 to 28 minutes or until a toothpick inserted comes out almost clean. A few crumbs or a little bit of batter are OK. The center will be soft.
If the top gets too brown you can lightly add aluminum foil to the top.
Transfer the bars from your baking dish to a cooling rack.
Allow the bars to cool for at least 1 hour or until completely cool before topping with the frosting.
To a bowl add the cream cheese frosting ingredients. Mix with a hand mixer on medium speed for 2-3 minutes or until fluffy.
Transfer the frosting to the bars. Evenly spread the frosting.
Cut into bars.