In a large skillet over medium heat, heat oil and butter. Add in garlic and rosemary and stir briefly until fragrant, 30 seconds.
Add in mushrooms and stir to coat evenly in butter. Season with salt and pepper, and continue cooking, stirring occasionally, until mushrooms are lightly golden, 6 to 8 minutes. Deglaze pan with water (or broth) and stir until fully evaporated.
Season with more salt to taste and top with more herbs before serving, if desired.
