Preheat oven to 325 °F (160 °C). Line a 12‑cup muffin tin with paper liners.

Combine crushed Oreo cookies and melted butter. Press about 1 Tbsp of this mixture into the bottom of each muffin cup to form the crust.

In a medium bowl, beat softened cream cheese and sugar until smooth and creamy.

Add the egg and vanilla extract; beat just until incorporated.

Mix in sour cream until the batter is silky smooth.

Gently fold in chopped Oreo pieces.

Spoon the mixture into each muffin cup, filling about ¾ full.

Bake 18–20 minutes, until the edges are set and the centers still jiggle slightly.

Turn off the oven, crack the door, and let cheesecakes cool inside for 30 minutes to avoid cracking.

Chill in the refrigerator at least 2 hours (or overnight) before serving. Top each mini cheesecake with a mini Oreo half or cookie crumbs just before serving.