Cover the base and sides of an 18 x 28cm slice tin with baking paper - make sure to leave paper hanging over the sides.
Melt the white chocolate in the microwave - cooking for 30 second spurts and once melted set aside to cool slightly.
Add the gelatine to a cup of boiling water and stir to combine.
Crush 250g of Oreo cookies either in a food processor, or with using a rolling pin until they resemble fine crumbs. Add the melted butter and stir to combine. Press the crumbs in the base of the slice tin and place in the freezer to chill for 30 minutes.
Using an electric mixer, combine the cream cheese, sugar and vanilla essence until smooth. Add the cream and mix to combine.
Stir through the gelatine mixture and white chocolate.
Chop the remaining Oreos into large chunks and stir through the cheesecake mixture.
Spoon the mixture over the chilled base and refrigerate for 3 hours or until the slice has set.