Preheat oven to 350 degrees. Butter or lightly spray with non-stick cooking spray a 9 x 13 baking pan. Place whole oreos in a single layer across the bottom of prepared baking pan. Set a side.
In a large bowl using an electric hand mixer, beat together until smooth 1/2 cup melted butter, dry cake mix, eggs, milk and 1/2 cup of crushed oreos (what's left from package). This will be a thick batter.
Pour cake batter over the top of oreos in the baking pan.
In a medium bowl blend together 4 oz cream cheese, 1/2 cup melted butter and 1 TBS vanilla extract. Add in powdered sugar 1 cup at a time and mix until creamy.
Using a large spoon place dollops of the cream cheese mixture onto cake batter. Using a butter knife, swirl the cream cheese mixture and the cake batter to create layers.
Place in preheated oven and bake for 35-40 minutes. Around the 25 minute time frame check to see if you need to loosely cover the cake with foil to keep top from browning to much.
Cool completely before serving. This can sit on your counter for the day, or refrigerate up to a few days because of the cream cheese.
