Preheat the oven to 320°F (160°C) and line a muffin tin with cupcake liners.

In a saucepan, combine cream cheese, unsalted butter, and whole milk over low heat. Stir until smooth and melted, about 5 minutes. Cool to room temperature.

In a bowl, sift together all-purpose flour, cornstarch, and salt.

In a separate bowl, whisk egg yolks with sugar until pale and creamy. Add the cooled cream mixture and lemon juice, whisking until combined.

Sift dry ingredients into the yolk mixture and fold gently until no streaks remain.

In a clean bowl, whip egg whites until soft peaks form. Gradually add granulated sugar and continue beating until stiff peaks form.

Fold egg whites into the batter in three additions, being careful not to deflate the mixture.

Pour batter into lined cupcake tins, filling each about 3/4 full, and gently tap to release air bubbles. Bake for 20-25 minutes until puffed and golden.

Cool in the tin for 5 minutes, then transfer to a wire rack. Dust with powdered sugar if desired before serving.