Preheat your oven to 320°F (160°C). Grease an 8-inch round cake pan and line the bottom with parchment paper.

In a large mixing bowl, beat the cream cheese until smooth. Add 1/4 cup of granulated sugar, butter, milk, and vanilla extract. Mix until well combined.

In a separate bowl, whisk the egg yolks. Gradually add the egg yolks to the cream cheese mixture, mixing until smooth.

Sift the flour, cornstarch, and salt into the cream cheese mixture. Mix until just combined and smooth.

In another bowl, beat the egg whites until soft peaks form. Gradually add the remaining 1/4 cup of granulated sugar and continue to beat until stiff peaks form.

Gently fold the egg whites into the cream cheese mixture in three additions, being careful not to deflate the batter.

Pour the batter into the prepared cake pan. Tap the pan gently on the counter to remove any air bubbles.

Place the cake pan in a larger baking dish filled with hot water to create a water bath. Bake for 60 minutes, or until the top is golden and the center is set but still slightly jiggly.

Turn off the oven and leave the cheesecake inside for an additional 15 minutes. Then, remove it from the oven and let it cool to room temperature.

Once cooled, refrigerate the cheesecake for at least 4 hours, preferably overnight, before serving. Dust with powdered sugar if desired.