In a large bowl, combine the egg yolks, brown sugar, cocoa, vanilla and salt. Whisk until combined and set aside.
Place chopped chocolate in a medium bowl. Heat the whipping cream in a saucepan over medium-high heat (or microwave for 1 1/2 minutes) until frothy and remove from heat. Pour over the chocolate and let sit for 5 minutes. Whisk until smooth. Add the egg mixture and whisk until combined and smooth.
Pour the mixture into a round 6- or 7-inch pan and cover with foil. Pour 1 1/2 cups water into the Instant Pot. Place pan on trivet and lower into Instant Pot.
Place the cover on the pot and set timer to 20 minutes on low pressure (pressure cook setting). It will take the IP around 7 minutes to build up pressure before it begins cooking.
When cooking time is done, let the pressure release naturally for 5 minutes and do a Quick Release. Let the float valve drop and remove the cover.
Stir pudding, cover with foil and refrigerate for a minimum of 2 hours before serving. Serve with whipped cream and chocolate shavings, if desired.
Store this pudding covered in the refrigerator for up to 5 days.