Preheat oven to 450 degrees F. Coat a rimmed baking sheet with cooking spray.Advertisement
Place mushroom caps, gill-side up, on the prepared pan. Sprinkle with salt and 1/8 teaspoon pepper. Roast until tender, 20 to 25 minutes.
Meanwhile, mash ricotta, spinach, 1/4 cup Parmesan, olives, Italian seasoning and the remaining 1/8 teaspoon pepper in a medium bowl. Place marinara sauce in a small bowl, cover and microwave on High until hot, 30 seconds to 1 1/2 minutes.
When the mushrooms are tender, carefully pour out any liquid accumulated in the caps. Return the caps to the pan gill-side up. Spread 1 tablespoon marinara into each cap; cover the remaining sauce to keep warm. Mound a generous 1/3 cup ricotta filling into each cap and sprinkle with the remaining 1/4 cup Parmesan. Bake until hot, about 10 minutes. Serve with the remaining marinara sauce.
Easy cleanup: Recipes that require cooking spray can leave behind a sticky residue that can be hard to clean. To save time and keep your baking sheet looking fresh, line it with a layer of foil before you apply the cooking spray.
2 vegetable, 1 medium-fat meat, 1 fat