01 -
Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper. Brush both sides of the mushroom caps with olive oil and place them gill-side up on the prepared baking sheet.
02 -
Bake the mushroom caps for about 10 minutes until they start to release water. This helps prevent a soggy final dish.
03 -
While mushrooms are pre-baking, heat remaining olive oil in a large skillet over medium heat. Add garlic and onion, cooking until softened, about 3-4 minutes. Add spinach and cook until wilted, about 2-3 minutes more. Remove from heat and let cool slightly.
04 -
In a bowl, combine the spinach mixture with ricotta cheese, Parmesan cheese, salt, pepper, and nutmeg if using. Mix well until thoroughly combined.
05 -
Spoon the cheese and spinach mixture evenly into the pre-baked mushroom caps. Top each with a portion of the shredded mozzarella cheese.
06 -
Return stuffed mushrooms to the oven and bake for 15-20 minutes more, until cheese is bubbly and golden brown.
07 -
Garnish with additional grated Parmesan cheese before serving. Enjoy while warm!