Preheat oven to 325 degrees. Prepare an 8×8 baking pan with non-stick spray. You may line the pan with foil or parchment paper for easier removal; spray the liner with non-stick spray.
Start by melting the chocolate in a microwave safe dish. Cook for 30 seconds, stir the chocolate and cook for another 10 seconds if needed. Set aside to cool.
Using a food processor, crush up the oreos until they are in fine pieces. Add in the melted butter and process again until all of the oreos are coated.
In a large bowl, beat the cream cheese, sugar and vanilla until smooth and creamy. Add in the sour cream and mix again. Add eggs, one at time and mixing well after each egg.