Step 1:Prepare the Mushrooms

• Preheat your oven to 375°F (190°C).
• Clean the portobello mushrooms with a damp cloth and remove the stems and gills using a spoon. Brush the mushrooms with 1 tablespoon of olive oil and place them on a baking sheet, gill side up.

Step 2:Make the Filling

• Heat the remaining 1 tablespoon of olive oil in a skillet over medium heat. Add the chopped onion and cook until it becomes translucent, about 3-4 minutes.
• Add the minced garlic and chopped red bell pepper to the skillet. Cook for another 2-3 minutes until the vegetables are softened.
• Stir in the chopped spinach and cook until wilted, about 2 minutes.
• Remove the skillet from heat and add the breadcrumbs, grated Parmesan cheese, shredded mozzarella cheese, chopped sun-dried tomatoes (if using), dried oregano, dried basil, salt, and pepper. Mix until well combined.

Step 3:Stuff the Mushrooms

• Divide the filling mixture evenly among the portobello mushrooms, pressing it down slightly to ensure it stays in place.

Step 4:Bake the Mushrooms

• Bake the stuffed mushrooms in the preheated oven for 20-25 minutes, or until the mushrooms are tender and the filling is golden brown.

Step 5:Serve

• Remove the mushrooms from the oven and let them cool slightly.
• Garnish with freshly chopped parsley before serving.