1. Preheat the oven to 425°F (220°C) to ensure even baking.
2. Gently clean each Portobello mushroom cap with a damp paper towel, avoiding water to prevent moisture absorption.
3. Remove the stems and scrape out the gills to create space for the filling.
4. Heat 1 tablespoon of olive oil in a skillet over medium heat and sauté your chopped vegetables until softened, about 5 minutes. Add any optional protein, cooking it fully before mixing.
5. Stir in your preferred herbs, spices, and cheese to create the flavorful stuffing mixture.
6. Place the cleaned mushroom caps on a parchment paper-lined baking sheet and brush each cap with olive oil. Season lightly with salt and pepper.
7. Fill each mushroom cap with the prepared stuffing, ensuring the contents are pressed gently into the cavity.
8. Sprinkle the tops with bread crumbs for added texture and crunch.
9. Transfer the baking sheet to the oven and bake for 10 to 15 minutes or until the cheese is melted and the tops are golden brown.
10. Remove the mushrooms from the oven and let them cool for a few minutes before serving.
11. Serve the stuffed Portobello mushrooms as a main course or a hearty side dish, optionally pairing them with complementary recipes like creamy chicken or fresh salads.