2. Step
Meanwhile, heat oil in a large skillet over medium heat. Add mushrooms and Brussels sprouts and cook, stirring often, until the mushrooms release their liquid, 8 to 10 minutes. Add garlic and cook, stirring, until fragrant, about 1 minute. Add sherry (or vinegar), scraping up any brown bits; bring to a boil and cook, stirring, until almost evaporated, 10 seconds (if using vinegar) or about 1 minute (if using sherry).