Remove the stems from the mushrooms and finely chop. Set aside.
Using your fingers, remove the skin off the mushrooms. Discard the skin.
Preheat the oven to 350F and prepare a baking tray lined with slightly greased foil or parchment paper.
To prepare the stuffing, saute the onion in olive oil on medium heat for about 4-5 minutes. Add the reserved chopped mushrooms, saute for another 3 minutes, and add garlic. Cook the garlic for another minute and turn the heat off.
Break the bread into small pieces and process in a small electric chopper or food processor until breadcrumbs form. Transfer the breadcrumbs into the mixing bowl. Add the sauteed onion, parsley, dill, and a touch of salt and pepper. Mix everything together.
Place the mushrooms onto the baking tray and top them with the breadcrumb mixture.
Bake for about 20-25 minutes, or until the mushrooms are tender and the breadcrumbs are golden. Serve with lemon wedges.
[nutrition-label]NOTE: You may use slightly stale white bread (ideally Italian loaf) or your favorite bread.