Infuse the milk with the vanilla or vanillin by heating it to almost boiling and then turning it off.
While the milk is cooling, in your widest sauté pan, add the sugar and turn the flame to high and wait. DO NOT STIR – at most, pick up the pan and swish it around to make sure the sugar is evenly melted in the caramel. As soon as almost all of the sugar has turned to caramel turn off the heat. With the other hand, pour a little caramel in the bottom of the form and twirl it around covering the form internally and on the sides as much as you can.
Using a fork or a whisk, mix 4 whole eggs plus one yolk with the sugar. Add the cooled, infused milk. Mix well. Fill the forms by pouring or using a soup ladle, leaving 1/2″ or 1 cm space from the top. Cover the forms with tinfoil.
Add adding two cups of water and the trivet or collapsible steamer basket to the cooker. Place as many forms as possible that will stay straight.
Close and lock. Turn the heat to high. When pressure is reached, turn the flame down and cook for 10 minutes at high pressure. Release the pressure.
Check for doneness by sticking a toothpick in the middle of one of the crèmes. If it comes out dirty, simply place the pressure cooker cover back on and wait another 5 minutes- the residual heat from the pressure cooker will keep cooking them. If the crème caramels are still liquid, cook under pressure an additional 5 minutes.
Let your crème caramels cool outside the cooker for about 1 hour before refrigerating.
Refrigerate for at least 3 hours before serving. If you need to do another batch, remember to add more water in your pressure cooker.
To serve, simply turn the form upside-down onto each dessert dish. If the Crème Caramel does not come down on its own, insert a flat knife and run it carefully along the sides. Then, on one side pull the knife a little towards the center to break the suction. Place the dessert plate on top of the form and flip it around quickly.