Preheat oven to 320°F (160°C). Line a 12-cup muffin tin with liners. Prepare a large roasting pan for a water bath.

In a small saucepan over low heat, gently melt cream cheese, butter, and milk, whisking until smooth. Remove from heat and let cool until lukewarm.

Once lukewarm, whisk in the 4 egg yolks, one at a time, then whisk in the vanilla extract.

Sift the all-purpose flour and cornstarch together into the cream cheese mixture. Whisk gently until just combined and smooth.

In a separate, large, clean bowl, beat the 4 egg whites and lemon juice with an electric mixer until foamy.

Slowly add the 1/2 cup of granulated sugar while beating. Continue to beat on high speed until stiff, glossy peaks form.

Gently fold the meringue into the yolk batter in three batches using a spatula. Stop folding as soon as no white streaks remain.

Divide the batter evenly among the 12 cupcake liners. They will be quite full.

Place the muffin tin inside the large roasting pan. Carefully pour hot water into the roasting pan to come 1-inch up the sides of the tin.

Bake for 20-25 minutes, until puffed, golden brown, and a skewer comes out clean.

Turn off the oven and crack the door open. Let the cupcakes cool in the oven for 15-20 minutes to prevent sinking.

Remove from the water bath and cool completely on a wire rack. Dust with powdered sugar before serving.