1. Beat egg whites until stiff peaks form. Add granulated sugar, incorporating a bit at a time. Set aside.
2. In a separate bowl, beat dessert topping until stiff peaks form. Add yolks, vanilla sugar, and dissolved coffee. Fold in egg whites.
3. Remove pies from the freezer and spread topping over the filling, dividing it evenly between the pies. Sprinkle with Viennese crunch and return to the freezer until ready to serve.
4. Optional- Pipe some whipped cream around the edge of the pie before serving.
Ostreicher’s cookies have a very different texture than other chocolate chip cookies and therefore result in a different pie crust. If they are not available near you, use chocolate chip cookies with as fine and smooth a texture as you can find.