Unless you are prepared to build some industrial strength equipment of your own design and then move everyone in the neighborhood away while you experiment with this, I fear you are taking your life in your hands.
Normal pressure cookers add a maximum 15 PSI to achieve a water boiling point of 121 C or 250 F. Autoclaves, used for surgical sterilization, go to 30 PSI. You are talking about going more than twice that.
There is no reason, based on the science of Maillard reaction, to believe that it would not occur at a high enough temperature. The presence of excess water would normally inhibit the process because of temperature reduction, but your "super duper pressure cooker" would keep the temperature at a high enough level to allow the chemical breakdown to occur. You might, in fact, discover that it occurs a bit earlier, as water tends to facilitate many reactions. Caramel making comes to mind as an indicator of what might be achieved, as sugar syrup (OK, most of the water is gone, but in principal) browns when you get in the above 330F-165C degree range.
As to crisping based on quick pressure reduction (perhaps when your device explodes?) That seems less likely as most crisping comes at the loss of water, and you are, in effect, keeping water in contact with your food both in liquid and superheated steam form. It would, most likely, be similar to a braised food surface, than a fried one.
Interesting thought. Please don't try this.
While movie theaters do often add flavoring agents (e.g. Flavacol) during cooking, that's not all they do for seasoning— they also use popcorn salt which is simply extremely finely ground plain salt. Morton, among other salt companies, package it for sale in grocery stores. It sticks perfectly to popcorn with absolutely no liquid or fat whatsoever. If you can't find any, and don't feel like ordering it online for some reason, putting salt into a high speed blender, spice grinder, mortar and pestle, or some other grinding device does the trick.
For a sweeter corn, you can use a shake of confectioners sugar. It would be great with a shake of cinnamon.
I love to add a touch of garlic powder and a shake of smoked paprika to mine! My wife absolutely swears by brewers yeast for her popcorn... she even brings a little jar of it with her to the movie theater.
Good luck and happy popping!
Best Answer
I never tried it, but I don't think it is a good idea.
The point of popcorn popping is that you cook the inside of the kernel within its hard shell until the internal pressure increases so much that it breaks the shell, releasing the starchy liquid inside as a foam. You need a pressure gradient, with higher pressure inside the kernel than on the outside. So, introducing high pressure outside the kernel is counterproductive. It will certainly result in more duds. I don't know if some kernels will be able to pop, but if yes, I expect them to take longer to pop, and create a denser foam, not light and airy popcorn. So, while I guess you could experiment with it if you don't have anything better to do, theory predicts that the experiment outcome won't be good.
Why did you want to try it at all? Popcorn doesn't take long to pop.