Preheat your oven to 400°F (200°C).

Carefully wipe each Portobello mushroom with a damp cloth to remove any dirt. Remove the stems and gently scoop out the gills to create a cavity for filling.

In a skillet over medium heat, sauté your chopped vegetables with a splash of olive oil and seasonings for about 5-7 minutes until tender. Mix in cheese and breadcrumbs until well combined.

Generously spoon the vegetable-cheese mixture into each mushroom cap, pressing down gently.

Place stuffed mushrooms on a baking sheet and bake for 25 minutes, until cheese is melted and mushrooms are tender.

Remove from oven, let cool for a minute, serve hot, and garnish with fresh herbs if desired.