Preheat your oven to 320°F (160°C). Line a muffin tin with cupcake liners.
In a medium saucepan, combine the cream cheese, unsalted butter, sugar, and milk. Heat over low heat, stirring until the mixture is smooth and well blended. Remove from heat and stir in the vanilla extract.
In a separate bowl, whisk together the egg yolks, cake flour, cornstarch, and salt until well combined. Gradually pour the cream cheese mixture into the egg yolk mixture, stirring continuously until smooth and homogeneous.
In another bowl, beat the egg whites with the cream of tartar until soft peaks form. Gradually add the remaining sugar and continue beating until stiff peaks form.
Gently fold the egg whites into the cream cheese mixture in three additions, being careful not to deflate the batter. The mixture should be fluffy and light.
Divide the batter evenly among the prepared cupcake liners, filling each about 2/3 full.
Place the muffin tin in a larger baking dish filled with about an inch of hot water to create a water bath, which helps the cupcakes steam and maintain their fluffiness.
Bake in the preheated oven for 25-30 minutes, or until the tops are lightly golden and a toothpick inserted in the center comes out clean.
Once baked, carefully remove the tin from the water bath and allow the cupcakes to cool in the pan for about 10 minutes before transferring them to a wire rack to cool completely.
Dust with powdered sugar before serving for an elegant touch, if desired.
Notes
Dust with powdered sugar before serving for an elegant touch.