Maybe it’s a par-braise? Not sure.
In any case, here’s the essence:
When you’re cooking something that has it’s own residual moisture, use that moisture (instead of additional fat) to help cook the items by putting a lid on your pan.
2 good examples I’ve used this on recently are mushrooms and onions. Toss a bit of olive oil or butter in a pan, add the veggies and cook for a bit, then lid the pan. Because the environment gets so steamy you’ll actually be able to cook the vegetables more than you would have (for the things like mushrooms and onions, where ‘cooking more’ is more virtue than crime) without them starting to stick and burn.
Mushrooms in particular are known for absorbing any fat you throw in the pan, then, as you cook, spitting it back out, and getting greasy.
Capturing the water vapor (deliciously flavored water vapor, I might add) and using that to keep everything nicely lubricated solves that problem.
Then, at the end of the process, when you’re close to the texture you want, pop the lid off, and let that little bit of fat you added in the beginning do it’s magic and brown things all up.
I’m curious to see if this works with other ‘superabsorbers’ like eggplant, but that’s for another day.