Preheat the oven to 325°F (163°C) and line a 9×13-inch baking pan with parchment paper, leaving an overhang on two sides.
Crush the Oreo cookies into fine crumbs and mix with the melted butter. Press the mixture firmly into the prepared pan.
Bake the crust for 10 minutes, then allow it to cool slightly.
Heat the whipping cream until steaming, pour it over the chopped white chocolate, let it sit for 2 minutes, then stir until smooth.
Beat the cream cheese until smooth. Add the sugar and cornstarch and mix until combined.
Stir in the melted white chocolate mixture, then add the eggs one at a time, mixing on low speed just until incorporated.
Pour the filling over the crust and bake for 35–40 minutes, until the edges are set and the center still has a slight jiggle.
Cool completely, then refrigerate for at least 4 hours or overnight.
To make the ganache, heat the cream until steaming and pour it over the chopped chocolate. Let it sit for 2 minutes, then stir until smooth and glossy.
Spread the ganache over the chilled cheesecake, refrigerate for 15–20 minutes, then slice into 15 bars and serve.