Start by gently wiping the mushroom caps clean, ensuring they are free from any debris. Make sure to completely remove the stems.
Give the roasted red pepper a thorough rinse and then gently pat it dry. Proceed to slice it into thin, elegant strips.
For the cooking process, position the oven rack in the lower one-third of the oven, and preheat it to 450°F (232°C). Line a baking sheet with foil for easy cleanup. Take the mushroom caps and toss them with oil, salt, and pepper until evenly coated. Place them gill side down on the prepared baking sheet, ready for roasting. Let them roast for approximately 25 minutes or until they release their juices and slightly shrink in size.
Once roasted, carefully take the mushroom caps out of the oven and allow them to cool slightly. When they are cool enough to handle, flip them over, and proceed to fill them with cheese, topping them with a few strips of the prepared red pepper. If you prefer to pause here, cover the filled mushrooms and refrigerate them for up to 2 days. Keep in mind that you may need to add a couple of extra minutes to the cooking time when you decide to bake them later.
When you’re ready to serve, bake the mushrooms until they are heated through, and the cheese is delightfully melted and bubbling, which should take around 20 minutes. Carefully transfer them to a serving platter, and for a finishing touch, sprinkle them with fresh parsley. Allow the mushrooms to rest for 5 minutes before serving, letting the flavors settle and meld beautifully.