Preheat the oven to 325°F / 163°C and crush 18 Oreo cookies into fine crumbs, then mix with melted butter and press into the bottom of a 9-inch springform pan.
Beat the cream cheese and sugar until smooth, then add sour cream, eggs one at a time, and vanilla extract, mixing just until combined.
Chop the remaining 6 Oreo cookies into chunks, fold into the batter, then pour over the crust.
Bake for 55 to 60 minutes until the edges are set but the center still jiggles slightly, then turn off the oven and let the cheesecake cool inside with the door cracked for 1 hour.
Refrigerate for at least 4 hours or overnight until fully chilled and firm.
Top with whipped cream and additional Oreo pieces before slicing and serving.