Combine flour and salt in a large bowl and add chopped cold butter. Use a fork to break the mixture into crumbs, then add cold water and knead into a dough.
Divide the dough into two equal parts. Turn one part over onto a clean surface and roll it into a circle. Repeat with the other part.
Preheat oven to 180 degrees.
Combine eggs, cottage cheese, apples, sugar, butter, cinnamon and cornstarch in a large bowl and mix well.
Place one circle of dough into a round baking pan and spread the apple mixture over it.
Place the second circle of dough on top of the filling so that both circles are connected.
Crack the egg into a bowl and beat it lightly, then brush it over the top of the dough.
Bake the cheesecake until golden brown, 50–60 minutes.
Mix the cream with powdered sugar and serve with the cheesecake as a sauce.