Wash and trim a packet of button mooshrooms, then cut them neatly into halves.
Peel, split and deshoot an appropriate amount of garlic. This recipe is called "mushrooms with garlic and vinegar", so don't think you can skimp on the garlic. I tend to use a full head of garlic per 400g (two packs) of mushrooms, and no one has ever complained, including my vampire friends. They know the score.
Get the garlic cloves into a mortar (as in, and pestle) with a healthy pinch of sea salt, and mush them up all good likes.
Add herbs. About a tablespoon of lovage is good. Parsley is traditional, but fuck that, because lovage is far superior. I've tried adding other herbs and/or spices at this stage, and it doesn't help. KISS.
You can do this bit directly into the mortar. Add about half a cup of vinegar. White wine vinegar is suggested, but I like to use about four parts apple cider vinegar (with the mother left in, go on, you know you want to) and one part black Chinkiang vinegar, to give it a bit of fermented malty goodness.
Get a frying pan reasonably hot with a good healthy glug of olive oil in there.
Throw in them mooshrooms. Toss them about so all of that oil gets absorbed. Now let them cook for a little while on the offside.
Flip them all so they are cut side down. Cut side down. This bit's important. Now let them cook for a while on this side. You want ten--fifteen minutes, depending on the temperature of your pan.
Leave them where they are for a bit. No fiddling. Five minutes, probably ten, depending on your pan and how well they absorbed that oil. What you're looking for is a nice crust on the cut side of your mooshrooms.
Now, throw in there all of that delicious vinegar-garlic mixture. Mix it around a bit, but gently, so that the mooshrooms all remain cut side down.
Let them cook until all of that delicious sauce is absorbed. Shoogle them around gently (gently!) every once inna while if you feel that you must, but do not disturb their orientation.