Warm the Cream: Pour the heavy cream into a microwave-safe bowl and heat for 45 seconds until slightly warm.
Mix the Custard: In the same bowl, whisk in the egg yolks, sugar, nutmeg, cinnamon, and vanilla extract until fully blended.
Prepare Ramekins: Divide the mixture evenly into four 8-ounce ceramic ramekins and cover each with foil.
Set Up Instant Pot: Pour 2 cups of water into the Instant Pot and place a trivet inside.
Arrange Ramekins: Stack the covered ramekins in two layers on the trivet in a crisscross pattern.
Pressure Cook: Secure the lid, set the valve to "Sealing," and cook on High Pressure for 15 minutes. Let the pressure release naturally for 15 minutes, then perform a quick release. Let the ramekins rest in the Instant Pot for 5 more minutes before removing.
Chill the Custard: Uncover the ramekins and refrigerate for at least 4 hours (preferably overnight) until firm.
Caramelize the Sugar: Sprinkle 1 tablespoon of sugar over each chilled custard and use a culinary torch or broiler to caramelize the top until golden and crisp. Serve immediately.