Preheat the oven to 375°F
Clean the mushrooms and remove the stems
Finely chop the stems
Heat oil or butter in a skillet
Sauté chopped stems with garlic and onion
Add breadcrumbs, cheese, herbs, salt, and pepper
Mix until the filling is combined
Brush the mushroom caps with oil
Fill each mushroom cap with the stuffing
Place the stuffed mushrooms on a baking sheet
Bake for 15 to 20 minutes
Broil for 1 to 2 minutes if you want a browned top
Serve warm