Don't wash the mushrooms, but you can wipe them with a moist paper towel if desired. Remove stems from mushrooms and cut the caps into ½" cubes.
Heat a large pan on medium heat, and add the butter and oil. Add the garlic but don't let it brown. Add a pinch of salt and pepper each, or to taste.
Add the mushrooms. They will lose a lot of water initially, which will need to evaporate. Once the mushrooms become tender, add parsley, mix, and adjust salt and pepper if needed. Cook for another minute, then serve.
This is delicious on its own or with any meat. It also goes well with quinoa. (Recipe♦420)