Mix pizza crust like pie crust, with the flour, salt and shortening. Add the egg yolks, lemon juice and water. Divide dough in half. Roll out as thin as possible and place on cookie sheet.
Lay 8 finely chopped apples on dough and sprinkle with the sugar, flour and cinnamon. Cover with remaining dough and pinch sides. Bake at 375 degrees for 45 minutes.
Mix together the frosting ingredients and spread on top of the pizza while still hot, after removing it from the oven. Serve.