Heat a non-fan oven to 320°F. Grease an 8-inch solid round pan about 3 inches deep. Line the base and sides with parchment, leaving a collar about 1 inch above the rim. Place it inside a larger roasting pan.

Over gently simmering water, stir cream cheese, butter, and milk in a heatproof bowl until smooth. Remove and cool to lukewarm. Mix the vanilla and yolks into the lukewarm base. Pass the flour and cornstarch through a sieve with the salt, then incorporate them until smooth.

Whip egg whites in a clean dry bowl until foamy. Gradually add all ½ cup sugar and beat to glossy soft-to-medium peaks whose tips bend.

Fold one third of the meringue into the cheese mixture. Fold the remainder in two batches with broad gentle strokes and pour into the lined pan.

Position the roasting pan in the oven. Carefully pour hot water around the cake pan to about 1 inch deep, keeping below its rim. Bake 60–80 minutes, until the center is set with only a slight jiggle, a skewer has no wet batter, and the center reaches at least 160°F.

Switch off the oven. Carefully lift the cake pan from the hot water and return it to the oven rack with the door ajar for 30 minutes. Transfer to a rack for about 60 minutes, then refrigerate within 2 hours after baking.

Chill at least 4 hours before unmolding and slicing into 8 portions. Cover and keep refrigerated.