Rinse mushrooms to remove any dirt and pat dry with a paper towel. Trim any extra long mushroom stems.
Add butter and olive oil to a large pan over medium-high heat. Let heat until butter is melted.
Add mushrooms and sprinkle with salt and pepper.
Let mushrooms cook for 5-7 minutes, stirring infrequently to allow mushrooms to brown and caramelize.
Reduce heat to medium and add garlic, thyme, and parsley. Cook for 1-2 minutes, until fragrant.
Toss everything well in the pan, then add to a serving dish, making sure to pour remaining pan drippings over top.
Sprinkle with remaining parsley for garnish and serve warm.