About an hour before you begin your recipe pull the eggs, ricotta, and cream cheese out of the refrigerator to get them to room temperature.
Add one cup of water to the cooker and add the trivet and set aside.
Grab a square of softened butter and rub it around the bottom and edges of a heatproof dish that will fit inside the cooker, set aside.
In a small pan, melt the butter. Meanwhile, pulverize the biscotti in a food processor. Pour in the melted butter and pulse a few times to incorporate.
With the back of your fingers or a spoon press the crumbs into the bottom of the heatproof dish to form a layer no thicker than ¼ inch thick. If you have extra crust, press it going up the sides as well. Place the container in the refrigerator to solidify the crust while you move on to the next steps.
In a mixing bowl with a hand blender, or with a fork stirring vigorously, break-up and mix the ricotta. Then, add the cream cheese and sugar. A little at a time, add the limoncello, vanilla, and lemon zest.
When everything is mixed together, add the beaten eggs. The result will be the consistency of a very runny pancake batter.
Take the cookie-crumb crust container out of the refrigerator, and delicately pour the cheese mixture over the crust. Lower this into the pressure cooker un-covered. Close the lid and set the valve to the pressure position.
For stovetop pressure cookers, cook on HIGH pressure for 15minutes. For electric pressure cooker users, cook on HIGH pressure for 20 minutes.
When time is up, open the pressure cooker using the natural release method. Electric pressure cookers: Turn off the cooker and wait until the pressure indicator has gone down (about 20 to 30 minutes). Stovetop pressure cookers: Move the cooker off the burner and wait for the pressure to come down on its own (about 10 minutes).
Delicately remove the container and place it on a cooling rack. Let the cake rest uncovered for about an hour and then refrigerate for another hour.
Once the cake has cooled, top it with a flat plate and flip it out. It will be upside-down, so all you need to do is to cover the bottom with the serving dish and flip one last time. Serve.