Stir together the brown sugar, cinnamon, and melted butter. Set aside.
Preheat the oven to 350 degrees F. Spray a 9”x13” pan with cooking spray or coat with butter.
With a mixer, beat together the 11 T butter and sugar for 2 minutes on medium high speed, until light and fluffy.
Stir in the sour cream and milk.
Beat the eggs in one at a time. Stir in the vanilla.
In a separate bowl, whisk together the flour, baking powder and salt.
Slowly mix the dry ingredients into the wet ingredients, mixing to combine between each addition of the dry ingredients.
Pour into the prepared pan.
Drizzle the cinnamon sugar topping over the top, the use a knife or toothpick to swirl and slightly mix the topping into the cake batter.
Bake for 25-30 minutes, or until the top is set and a toothpick can be poked into the cake and come out clean.
Allow to cool completely while making the frosting.
In a mixer, whip together the butter and cream cheese for 2 minutes on high, until light and creamy.
Slowly add in the powdered sugar, a little at a time, until completely incorporated.
Stir in the vanilla and salt, then whip until everything is mixed together completely.
Place dollops of frosting on the dessert bars, then spread the frosting smooth with an offset icing spatula or the back of a spoon. Cut into slices and enjoy! https://amzn.to/2QbVPjv
Cover with plastic wrap and store in the fridge. Bring to room temperature before serving again.