Preheat oven to 350 degrees Fahrenheit. Line a baking sheet with Gefen Parchment Paper.

In a saucepan over low heat, combine the sour cream, butter, and sugar until smooth. Pour into a large mixing bowl and add the water, yeast, eggs, and flour. Mix until a dough forms.

Divide in half and roll each piece into a rectangle measuring about 12×22 inches. Set aside.

Prepare the filling: In a bowl, mix together the granulated sugar, brown sugar, cinnamon, and vanilla sugar.

Brush the melted butter over the dough rectangles. Sprinkle the filling over the butter.

With a sharp knife, cut each rectangle into five to six triangles. The widest part of each triangle should measure four inches.

Starting from the bottom, roll up the triangles tightly and place on the prepared baking sheet.

Bake for 18–20 minutes. Drizzle with melted chocolate and serve.