1-First: whisk 2 tablespoons extra virgin olive oil, 1 tablespoon balsamic vinegar, and 2 cloves garlic, pressed, in a small bowl. Place 4 large portobello mushroom caps in a large, zipper seal plastic bag and add the marinade. Seal and flip the bag several times to coat, then let it rest for 15 minutes.

2-Next, preheat your oven to 450ºF and place the marinated mushrooms stem side down on a rimmed baking sheet. Bake for 10 minutes to start. In a medium bowl, combine 10 ounces frozen chopped spinach (defrosted and excess water removed), ¼ cup Parmesan cheese, and 2-3 tablespoons heavy cream. Season with coarse kosher salt and freshly ground black pepper to taste.

3-Remove the mushrooms from the oven and flip them. Divide the spinach mixture evenly over each mushroom, then top with 1 cup shredded mozzarella cheese and the remaining ¼ cup Parmesan cheese. Return to the oven for another 10 minutes or until the cheese melts and browns slightly. Serve warm, perhaps with sides like mashed potatoes or grilled vegetables for a complete meal.