Rinse whole mushrooms under cold water quickly and pat them dry with a paper towel right away.
Cut mushrooms into half, or quarter if they are very large, and add them to a mixing bowl.
Toss mushrooms in 1/2 tbsp. of oil to coat them and then add pressed garlic cloves, salt, pepper, and garlic powder. Mix well to coat mushrooms evenly.
Preheat the skillet first, over medium-high heat.
Add a tablespoon on oil and spread it around. Add mushrooms in an even layer and let them sauté, undisturbed, for a few minutes to get a nice sear on them.
Add butter and let it melt. Once butter is melted, mix mushrooms and let them sauté again, undisturbed. Keep mixing once in a while, but not too often, letting mushrooms get a sear each time. Depending on the size, it will take 7-10 minutes to cook mushrooms.
Once mushrooms are done, take them out and serve. Garnish it with some parsley if you'd like.