First layer: graham cracker cheesecake crust
In a bowl, mix graham cracker crumbs, melted butter, and sugar. Transfer the mixture to a non-stick removable loose bottom cake pan 20 cm or 8-inches. Press it firmly in the bottom of the pan. Place in the preheated oven. Bake for 10 minutes at 180 °C / 350°F. Remove from the oven and set aside to cool.
Second layer: Cream cheese
In a food processor mix together cream cheese, ricotta cheese, eggs, sugar, and vanilla sugar. Mix until the mixture becomes creamy and smooth. Pour the cream cheese mixture over the baked and cooled graham cracker cheesecake crust. Place the cheesecake with the two layers back in the oven. Place the pan on the middle rack and bake for 45 - 55 minutes at 150 °C / 300 °F or until the edges are solid and the center is still a bit jiggly and soft.TipIf you don't have a food processor, you can use a blender or hand-held electric mixer as well.
Third layer: Sour cream
Make the sour cream topping for cheesecake. In a bowl beat together sour cream, sugar and vanilla sugar. Beat until the mixture becomes creamy.
Bake and Serve
Take the baked cheesecake from the oven and let it cool for about 10 minutes. Then spread the sour cream topping evenly over the baked cake. Place back in the oven and bake for another 10 minutes at 150 °C / 300 °F. Remove the baked Cheesecake with sour cream topping from the oven. Bring the cheesecake to room temperature, then place in the fridge. Leave the cheesecake to set in the fridge for at least 4 - 6 hours, or even better, overnight. Place the cake onto a serving plate, slice and serve.