Käsekuchen - German Cheesecake

DIRECTIONS

• For the Crust:
• Sift the flour, stir in the baking powder, salt, vanilla-sugar, lemon peel and sugar, then rub in the butter and knead to a smooth consistency with the egg. (Can use Food Processor).
• Place dough in a plastic bag in the refrigerator for 1 hour.
• Preheat oven to 300 degrees F.
• You will need a 9 or 9 1/2-inch spring form pan.
• Roll out the dough on a well-floured work surface.
• Place dough in bottom of a 9 or 9 1/2-inch spring form pan, pressing it up the sides almost to the top. Set aside.
• For the Filling:
• Beat the egg yolks with the sugar and vanilla-sugar until pale and foamy. Add the softened butter and beat well, then add the heavy cream and beat again.
• Add the quark and stir until the mixture is smooth and thoroughly combined.
• Whisk the egg whites with the salt until very stiff, then very gently fold in the quark mixture, also adding the sifted cornstarch a little at a time.
• Pour the filling into the crust shell and gently wobble the pan back and forth until the surface is smooth.
• Trim the dough, leaving about 1 inch.
• Bake in preheated 300 degrees F oven for 50 to 60 minutes (longer if necessary) until well risen and golden - it resembles a soufflé at this point (It will sink in the middle quite dramatically - don't worry, it's supposed to do this).
• Turn the oven off, and let the cheesecake rest in the oven for 15 minutes; then remove it from the oven, cool for an hour or so at room temperature, and refrigerate for several hours before releasing sides of pan and serving.