Try finding small button mushrooms for this recipe. Rinse the mushrooms. Place them (stalks intact) in a large, wide pan over high heat.
Add olive oil, salt and pepper and shake the pan to disperse. Let the mushrooms sit undisturbed until they start to colour on the bottom.
Shake the pan a few times to ensure that the overlapping mushrooms touch the surface of the pan. Keep the heat on high the whole time.
When browned on both sides and all their juices have evaporated, add the garlic to the pan and cook for 30 seconds.
Pour in the sherry vinegar and turn the heat down to medium. Stir and cook until the vinegar evaporates and only just coats the mushrooms. Add parsley and butter and stir through for 1 min. Serve warm or at room temperature.