Stir cream cheese and milk together.
Then add in cornstarch, vinegar, half the sugar (about 2 tablespoons) and salt.
Add in egg yolks and mix. Set aside.
Whip up the remaining sugar (2 tablespoons) and egg whites until mixture becomes white with soft peaks. Stir in cream of tartar.
Pour half of the egg white mixture into the egg yolk batter and fold in. Repeat with remaining egg white mixture.
Pour batter into pan. If you are using a springform pan, make sure it is lined tightly with foil on the outside so that no water will leak in. Double it if you can!
Open Instant Pot. Place trivet, then add enough water to submerge pan halfway. Place pan on top of trivet.
Close Instant Pot. Select Pressure cook, 20 minutes on low pressure.
When done, wait 10 minutes before quick release. Remove from pan and serve.