Preheat oven to 350°F and add muffin liners to a 12-cup muffin tin.
Twist apart 6 Oreos and place one cookie on the bottom of each of the muffin cups.
In the bowl of a stand mixer, add the cream cheese. Beat until smooth.
Add the sour cream, eggs and vanilla and mix until smooth.
Crush 7 of the remaining Oreo cookies into the filling mixture; stir.
Scoop the filling into each of the 12 muffin cups.
Bake for 15-17 minutes or until the centers of each of the cheesecakes are JUST set. (Don't overbake!)
Let cool then top with a dollop of whipped topping.
Combine the chocolate chips and oil in a small bowl. Microwave on a low power level, stirring frequently until smooth.
Drizzle the chocolate over the mini cheesecakes.
Break the remaining cooking into 4 pieces each and press into the cheesecakes.
Refrigerate until ready to serve.