Grease a bowl with butter and add a square of greased baking paper to the bottom to stop it sticking. The bowl should be around 1.1 litre (2pints) and must fit in the instant pot.
Add all the pudding ingredients to a separate bowl and beat together with an electric mixer.
Spoon the mixture into the greased bowl and cover with tin foil.
Add the trivet to the instant pot and then make a sling using tin foil to lower the pudding onto the trivet.
Fill with cold water to approximately halfway up the height of the bowl.
Put the lid on the instant pot but do not seal (use a glass lid if you have one).
Set the instant pot on steam for 90 minutes.
When the time is up, remove the lid and then the pudding using the tin foil sling.
Drain the water from the instant pot and dry. Add the cream and milk to the pot and set to saute.
When it is boiling, add the chocolate and vanilla. Turn the pot off and stir until the chocolate has melted.
Remove the foil from the pudding and then turn out onto a plate.
Serve with the chocolate sauce on top and enjoy!