Clean mushroom caps (cremini or button), remove stems, and brush with olive oil. Sauté chopped mushroom stems with garlic and onion until soft, then add chopped spinach and cook until wilted. Squeeze out excess moisture and combine with cream cheese or ricotta, grated Parmesan, breadcrumbs, and herbs.
Spoon the filling into mushroom caps, sprinkle with extra cheese or panko, and bake at 375°F (190°C) for 12–15 minutes until golden and bubbling. Serve warm.
Tips:
These are easy to prepare ahead and finish in the oven just before guests arrive.