Preheat your oven to 400°F (200°C).

Gently wipe the Portobello mushrooms with a damp cloth to remove any dirt. Remove the stems by twisting them off.

In a mixing bowl, combine your choice of finely chopped vegetables, cheese, breadcrumbs, and herbs or spices to create the filling mixture.

Generously fill each Portobello mushroom cap with the mixture, pressing down lightly to pack it well.

Drizzle a little olive oil over the stuffed mushrooms to enhance their flavor while roasting.

Carefully place the baking sheet in the preheated oven and bake for about 25 minutes.

Once baked, remove the stuffed mushrooms from the oven and allow them to cool for a few minutes before serving.