In a mixing bowl, combine the heavy cream, 75 grams of sugar, vanilla extract, and a pinch of sea salt. Whisk until the sugar dissolves completely.
In a separate bowl, whisk the egg yolks until they are smooth. Gradually add the cream mixture to the egg yolks, whisking continuously to prevent the eggs from scrambling. If using passionfruit curd, fold it in gently at this stage.
Pour the custard mixture into the ramekins, filling them about ¾ full. This will allow space for the custard to expand slightly while cooking.
Pour 1 cup of water into the Instant Pot. Place the trivet inside, then carefully arrange the filled ramekins on top of the trivet. Make sure they are stable.
Seal the Instant Pot lid and set the valve to 'Sealing.' Cook on high pressure for 8 minutes. Once the cooking time is up, let the pressure release naturally for about 10 minutes before doing a quick release for any remaining pressure.
Carefully remove the ramekins from the Instant Pot and let them cool at room temperature. Once cooled, cover with plastic wrap and refrigerate for at least 4 hours or overnight.
When ready to serve, sprinkle about 1 teaspoon of white granulated sugar evenly over the top of each custard. Using a kitchen torch, caramelize the sugar until it turns golden brown and bubbly. If you don't have a torch, you can use the broiler in your oven; just keep a close eye on it to prevent burning.