In a double boiler, combine the cream cheese, butter, and milk.
Cool the mixture, then add the flour, cornstarch, egg yolks, and natural lemon extract, and mix.
Beat the egg whites until stiff. Add the sugar and beat.
Add the cream cheese mixture to the egg white mixture.
Using buttered baking paper, line a 20 cm springform pan, covering the bottom and sides generously. Pour in the final mixture, pressing down firmly to prevent bubbles from forming in the cake.
Cover the outside of the pan with three layers of aluminum foil, then place it inside a larger pie pan. Pour about 3 cm of hot water into the outer pan to create a water bath.
Place in the oven and bake for approximately 1 hour and 10 minutes at 160°C until the top crust is browned.
