Preheat your oven to 400°F (200°C). Make sure your oven is fully heated to achieve that perfect bake.
Prepare a baking sheet by spraying it lightly with olive oil. This will help prevent sticking and promote browning.
Gently remove the stems from the portobello mushrooms and scoop out the gills using a spoon. This creates a cavity for your delicious filling.
Spray the tops of the mushrooms with more olive oil, then season them with about an eighth of a teaspoon of kosher salt and fresh pepper to taste. This seasoning will elevate their natural flavor.
In a large nonstick sauté pan, heat over medium heat and add a tablespoon of olive oil. Once hot, toss in the onion, garlic, and red bell pepper. Season with another eighth of a teaspoon of kosher salt and cook until the vegetables soften, about three to four minutes.
Next, add the chopped baby spinach to the pan. Sauté until the spinach wilts, which should take about one minute. The vibrant green color is a sign that it's ready!
In a medium-sized bowl, combine the ricotta, parmesan cheese, and egg. Mix these together until well blended. This mixture is the heart of your stuffing!
Add the sautéed vegetables and chopped basil to the ricotta mixture. Stir well to ensure everything is evenly distributed.
Now, it's time to stuff those mushrooms! Spoon the ricotta filling into each mushroom cap, packing it in firmly to maximize the filling.
Top each stuffed mushroom with about two tablespoons of marinara sauce and sprinkle on two tablespoons of mozzarella. This layer will create a delicious gooey top.
Place the stuffed mushrooms on your prepared baking sheet and bake them in the preheated oven for 20 to 25 minutes. You’ll know they’re done when the tops are bubbly and golden.
Once baked, remove them from the oven and garnish with additional basil if desired. Serve warm and enjoy each flavorful bite!
