Prepare the Baking Pan : Preheat your oven to 160°C (320°F). Grease a round springform pan and line the bottom with parchment paper. Wrap the outside of the pan with foil to make it watertight, as the cake will be baked in a water bath.

Make the Cheesecake Base : In a medium saucepan over low heat, combine the cream cheese, butter, and milk. Stir until smooth and remove from heat. Let the mixture cool slightly, then whisk in the egg yolks and vanilla extract.

Combine Dry Ingredients : Sift the flour and cornstarch into the cream cheese mixture. Whisk until fully incorporated, ensuring no lumps remain.

Beat the Egg Whites : In a separate bowl, beat the egg whites with the cream of tartar using an electric mixer. Slowly incorporate the sugar while continuing to beat, until stiff peaks begin to form.

Fold the Mixtures : Gently fold one-third of the egg whites into the cream cheese mixture to lighten it. Gently fold in the rest of the egg whites, taking care not to deflate the mixture.

Bake the Cheesecake : Pour the batter into the prepared pan. Set the pan into a larger baking dish and add hot water around it, ensuring it reaches about 1 inch deep to create a water bath. Bake at 160°C (320°F) for 60-70 minutes, or until the top is lightly golden and the cake jiggles slightly in the center.

Cool and Serve : Turn off the oven and leave the cheesecake inside for 10-15 minutes with the door slightly ajar to prevent cracking. Take it out of the oven and allow it to cool completely. Refrigerate for at least 2 hours before serving. Dust with powdered sugar for a finishing touch if desired.