Grease 4-ounce ramekins. In the inner liner of your Instant Pot, add one cup of water and the trivet.

In a medium saucepan, whisk together the cream, half and half, and sweetener. Heat over medium heat until simmering.

Remove the pan from heat. Add the chopped chocolate and vanilla extract. Whisk until melted and smooth.

In a medium bowl, whisk together the egg yolks and salt. Slowly pour the chocolate mixture over the egg yolks, whisking constantly to combine.

Divide the custard among ramekins. Cover with foil and seal tightly. Place the ramekins on the trivet in the Instant Pot, stacking.

Close and lock the lid. Set the valve to sealing. Set the pressure to High Pressure and set the timer for 6 minutes. When the time is up, do a natural pressure release for 15 minutes and then release to release any remaining pressure.

Transfer the cups to a wire rack. Uncover and let cool. Cover with plastic wrap and chill 4hours to overnight before serving.