Preheat oven to 350 degrees F (175 degrees C). Grease two 9 inch round cake pans.
Make cake per directions except substitute the 1 1/2 cups of strawberries for the water and add 1 extra egg, (if cake mix calls for 2 eggs add 3), and 8 ounces of the cream cheese at room temperature. Beat well and pour into the prepared pans.
Bake at 350 degrees F (175 degrees C) for about 20 to 25 minutes or until golden brown. A toothpick inserted in the center will not come out clean when this cake is done since it is so moist. Let cake cool fully before frosting.
To Make Frosting: Heat the heavy cream until just beginning to boil. Pour it over the white chocolate (chopped) and the remaining 4 ounces cream cheese. Mix well and let cool. Once cool fold into the whipped topping. Use to frost cooled cake and garnish with sliced fresh strawberries.
Working with a compact oven requires careful pan placement to ensure two nine-inch round layers bake evenly without crowding the heating elements. This build alters standard box ratios by substituting pureed fruit for water, which yields a dense, pudding-like crumb. Managing this added moisture demands specific techniques for mixing and temperature control.
Moisture Control and Mixing Technique
Incorporating pureed strawberries and softened cream cheese directly into the batter changes the internal structure significantly. Ensure the eight ounces of cream cheese reach absolute room temperature before beating, otherwise stubborn lumps will persist and disrupt the final crumb. Because of the exceptionally high moisture content, a toothpick test fails here; rely instead on a golden-brown surface and edges that pull slightly from the pan at 350 degrees F after 20 to 25 minutes.
Ganache Emulsification
The white chocolate frosting relies on a hot cream pour to melt the solids without scorching them. Heat heavy cream just until it begins to boil, then pour it over chopped white chocolate and the remaining four ounces of cream cheese. Whisk this mixture until smooth, and verify it drops to room temperature before folding in the thawed whipped topping to prevent the fat from breaking.
Cooling and Layer Integrity
Thermal shock will melt the delicate frosting instantly, making complete cooling non-negotiable. Transfer the baked layers to wire racks for at least one hour until the pans register completely neutral to the touch. Once chilled, apply the white chocolate mixture and garnish with sliced fresh fruit.