Bake the cake according to the package directions, except substitute the 1-1/2 cups of pureed strawberries for the water, and add 1 extra egg (if the cake mix calls for 2 eggs, add 3 eggs) and mix in the 8 ounces of softened cream cheese (set aside the remaining 4 ounces of cream cheese for topping) beat until well combined.
Pour/divide into prepared cake pans.
Bake for about 20-25 minutes or until golden brown (a toothpick inserted in the middle will NOT come out clean as this cake is SO moist).
Let cool fully before frosting.
For the frosting; heat the whipping cream until JUST beginning to boil.
Pour it over the white baking chocolate (chopped), and add the remaining 4 ounces of cream cheese; mix well, and let cool completely.
Once cool gently fold into the Cool Whip thawed topping.
Frost the cake, and garnish with sliced fresh strawberries.