Combine cornstarch and sugar in a small bowl. Add cream cheese, sugar, and cornstarch to a medium bowl. Beat until smooth, using a spatula to scrape down sides of bowl as you go.
In a microwave safe bowl, combine white chocolate chips and heavy cream. Microwave chips and heavy cream for 20-30 seconds, then whisk until completely smooth. If chips are not melted after one minute of whisking, microwave for 10 second intervals, stirring in between, until smooth. The time needed will vary depending on how warm your house is, and the wattage of your microwave. In a warm house with a high wattage microwave, 20 seconds will be all you need.
Let white chocolate mixture cool until warm, not hot, then fold into cream cheese mixture until completely combined.
Add eggs and vanilla and beat until just combined.
Remove cheesecake crust from freezer and pour batter into pan. (Optional: Tap pan gently against table/counter to bring air bubbles to the surface. Use a fork or toothpick to pop air bubbles.)
Add 1 ½ cups water and 3-inch trivet to Instant Pot. Cover cheesecake with foil, and place on trivet. Cook for 40 minutes at high pressure, then allow a natural pressure release.
Once pressure is released, turn off Instant Pot and carefully remove cheesecake. Remove foil and allow cheesecake to cool for one hour or until room temperature.
Once cool, carefully run a paring knife around the edge of the cheesecake to separate from pan, but do not remove from pan. Refrigerate for at least 6 hours, preferably overnight.
Carefully push cheesecake up from push pan by placing center of push pan on a can or glass and pushing edges down. If using springform pan, gently remove outer edge of pan.