01 - Preheat the oven to 375°F. Line a baking tray with parchment paper.
02 - Clean the mushroom caps and set aside. Finely chop the mushroom stems.
03 - Heat 1 tablespoon olive oil in a skillet over medium heat. Add the chopped mushroom stems and garlic; sauté for 2 minutes.
04 - Add the chopped spinach and cook until wilted, about 2–3 minutes. Remove from heat and let cool slightly.
05 - In a mixing bowl, combine the cooked spinach mixture, cream cheese, Parmesan, mozzarella, parsley, salt, black pepper, and red pepper flakes. Mix until smooth.
06 - Spoon the filling generously into each mushroom cap and arrange them on the prepared tray.
07 - Sprinkle breadcrumbs over the stuffed mushrooms and drizzle with olive oil.
08 - Bake for 20–25 minutes, or until mushrooms are tender and the tops are golden brown.
09 - Garnish with extra parsley and serve warm.