1. Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners.
2. In a food processor, crush the Oreo cookies until they form fine crumbs. Mix the crumbs with melted butter until well combined.
3. Spoon about 1 tablespoon of the cookie mixture into each muffin cup, pressing down firmly to create a base.
4. In a large mixing bowl, beat the cream cheese until smooth and creamy, about 2-3 minutes.
5. Add the sugar and vanilla extract to the cream cheese, mixing until fully incorporated.
6. Beat in the egg, ensuring that it is well mixed, followed by the sour cream.
7. Spoon the cheesecake mixture over the Oreo bases, filling each cup about 3/4 full.
8. Bake for 15-18 minutes or until the cheesecake has set. The tops should be slightly firm to the touch.
9. Allow the cookie cups to cool in the tin for about 10 minutes before transferring them to a wire rack to cool completely.
10. Chill in the refrigerator for at least 1 hour before serving.

One tip I learned from Mama Lou: always use room temperature ingredients for the filling to achieve a smoother texture.