Soak gelatin in cold water.
Whip the cream until lightly whipped.
Whip the sour cream, cream cheese, powdered sugar, and vanilla sugar together in another bowl.
Crush the Oreo cookies and mix them with the cheese mixture.
Melt the gelatin in a small bowl with the water clinging to it.
Add a spoonful of the cheese mixture to the gelatin and temper the gelatin. Add another spoonful and mix well.
Add the gelatin to the cheese mixture and mix well and quickly (whip quickly with a hand whisk if necessary).
Fold the lightly whipped cream in and spread the mixture over the base.
Refrigerate for at least 3 hours.