Preheat the oven to 180°C. Line an 18 cm cake pan with baking paper.
Finely crush the Oreo cookies for the crust. Mix them with the melted butter until evenly combined.
Press the crust mixture firmly into the base of the prepared pan. Bake for 10 minutes, then remove from the oven.
Reduce the oven temperature to 170°C.
In a mixing bowl, beat the cream cheese, mascarpone, sugar, and vanilla until smooth.
Add the heavy cream and eggs. Mix briefly on the lowest speed, or whisk gently by hand, just until combined.
Fold in the chopped Oreo cookies with a spatula.
Pour the filling over the baked crust and smooth the top.
Bake for 40–50 minutes at 170°C. The edges should be set and the center should still have a slight wobble.
If possible, place a small oven-safe pot of hot water in the oven next to the cheesecake while it bakes to create steam.
Let the cheesecake cool completely in the pan.
For the topping, heat the heavy cream until it just starts to boil.
Pour the hot cream over the broken white chocolate. Let it sit briefly, then stir until smooth.
Pour the white chocolate ganache over the cooled cheesecake.
Decorate with whipped cream, Oreo cookies, and raspberries if desired.
Chill in the refrigerator for 2–3 hours, preferably overnight, before slicing and serving.