Step 1

Preheat oven to 350°F (175°C). Grease a 10-inch springform pan.

Step 2

Process butter cookies in a food processor until finely ground. Stir in the melted butter until crumbs are evenly moistened.

Step 3

Press the buttered crumbs firmly into the springform pan, creating a slightly raised edge on the sides.

Step 4

In a large bowl combine softened butter, granulated sugar, vanilla sugar, custard (or pudding) powder, and eggs. Beat with an electric or stand mixer until smooth.

Step 5

Stir the quark and sour cream into the butter-egg mixture until fully incorporated.

Step 6

In a separate bowl whip the heavy cream to stiff peaks.

Step 7

Gently fold the whipped cream into the quark mixture until evenly combined.

Step 8

Pour the filling over the cookie crust and smooth the top.

Step 9

Place the springform pan on the center oven rack and set a cookie sheet on the rack below to catch any drips.

Step 10

Bake 50–60 minutes, or until the top is golden brown and the center appears set.

Step 11

Turn off the oven, prop the door open slightly, and let the cheesecake cool in the oven for about 1 hour.

Step 12

Remove the pan to a wire rack and let the cheesecake cool completely.

Step 13

Refrigerate for several hours, preferably overnight, before serving for best texture and flavor.