Heat the oil in a 12-inch skillet over high heat until it's hot and shimmering. Add the mushrooms, season with 3/4 teaspoon kosher salt, stir to coat in the oil, then let the mushrooms cook undisturbed until the liquid released by the mushrooms evaporates and they're deep golden brown, 5 to 7 minutes. Stir and continue sauteing, stirring occasionally, until most sides are nicely browned, 3 to 5 minutes more.

Reduce the heat to medium, add the garlic, and cook just to soften it, 15 to 30 seconds. Add the vinegar and stir, scraping the bottom of the pan, until the vinegar evaporates, about 15 seconds. Remove the pan from the heat and toss in the parsley. Season to taste with more salt, if you like. Transfer to a dish and serve with toothpicks for spearing the mushrooms or a serving spoon for putting on individual plates.