10ouncesfrozen chopped spinachdefrosted and excess water removed
1cupshredded mozzarella cheese
Coarse kosher salt and freshly ground black pepper
In a small bowl, whisk together olive oil, balsamic vinegar, and garlic.
Place mushroom caps in a large, zipper seal plastic bag and add the olive oil marinade. Seal the bag and flip it over a few times to distribute the marinade over the mushrooms. Allow to rest for 15 minutes.
Preheat the oven to 450ºF. Place marinated mushrooms stem side down on a rimmed baking sheet. Bake 10 minutes.
Meanwhile, prepare the filling by combining spinach, 1/4 cup Parmesan cheese, and heavy cream in a medium bowl. Season to taste with salt and pepper.
Remove the mushrooms from the oven and flip. Divide the spinach filling over the mushrooms, then top evenly with mozzarella cheese and remaining parmesan.
Return the mushrooms to the oven for 10 minutes or until the cheese is melted and beginning to brown.
Serve warm with mashed potatoes, grilled veggies, or your other favorite sides.
A few ideas to customize your spinach stuffed portobello mushrooms: