1. Prepare a 7×3-inch or 8×3-inch cake pan with a pop-out bottom, or you can use any springform or cake pan. You will also need a deep pan (that the cake pan fits inside of) for the water bath. Line the bottom of the cake pan with Gefen Parchment Paper. Also line the sides of the pan with rectangular strips of parchment paper.
2. Place cream cheese, butter, sugar, and vanilla sugar in a pot over low flame and allow to melt. Mix until there are no clumps and you have a smooth mixture.
3. Remove from heat and add egg yolks into the cream cheese mixture. Mix well but gently.
4. Add flour and cornstarch. Mix well so there are no clumps.
5. Add milk and lemon juice and mix until mixture is smooth. Set batter aside.
6. In the bowl of an electric mixer, beat egg whites. When a little foamy, add cream of tartar. When egg whites become very foamy, add sugar. Continue beating until egg whites have stiff peaks. Peaks should hook over slightly; do not overmix until stiff, straight peaks form.
7. Preheat oven to 330 degrees Fahrenheit.
8. Fill a deep pan with water. (Make sure that there isn’t too much water so it won’t spill out once you add the cheesecake pan.) Place in the oven.
9. Add a little of the beaten egg white mixture into the cream cheese batter. Fold gently.
10. Repeat another two times.
11. Wrap two layers of aluminum foil around the bottom of baking pan (to keep the cake from getting wet). Pour batter into pan and place into the water bath.
12. Bake for 25 minutes. (You may have to adjust oven temperature if your cake is not rising. If necessary, raise by 10 degrees.)
13. After 25 minutes, open oven door for 10 seconds. Lower oven temperature to 245 degrees Fahrenheit and bake for another 45 minutes.
14. After 45 minutes, shut oven but leave cake inside for 10 minutes.
15. Remove from oven and from water bath. Cake should be jiggly. It firms when chilled. Remove cake from pan and plate.
16. Most Japanese cheesecakes are topped with confectioners’ sugar, but any of the topping ideas will do, especially if you like a sweeter cheesecake (Japanese cheesecakes are not as sweet as New York-style ones).