Preheat oven to 320°F (160°C). Line a 12-cup muffin tin with cupcake liners or grease and flour the cups.

In a saucepan, heat cream cheese, butter, and milk over low-medium heat, stirring until smooth. Let cool to room temperature.

In a separate bowl, whisk flour, cornstarch, and salt. Set aside.

In a large bowl, whisk egg yolks, granulated sugar, and lemon juice until pale and smooth. Add cooled cream cheese mixture and whisk to combine.

Sift in dry ingredients and mix gently until fully incorporated.

In a clean bowl, beat egg whites to soft peaks. Gradually add 2 tablespoons of sugar and continue to beat until stiff peaks form.

Gently fold a third of the egg whites into the batter. Then fold in the remaining egg whites, being careful not to deflate the mixture.

Fill muffin cups ¾ full with the batter. Tap the tin to release air bubbles.

Bake for 20–25 minutes or until tops are golden and slightly puffed.

Cool in tin for 5 minutes, then transfer to a rack. Dust with powdered sugar if desired and serve.