Start by cleaning the mushrooms. Gently wipe them with a damp cloth to remove any dirt. Carefully remove the stems and set them aside. You’ll need the caps for stuffing.
Chop the mushroom stems finely and add them to a mixing bowl. To this, add the drained clams, chopped green onion, beaten egg, minced garlic, garlic salt, Italian breadcrumbs, oregano leaves, melted butter, Parmesan cheese, Romano cheese, and mozzarella cheese for stuffing. Mix everything thoroughly until well combined.
Take the mushroom caps and fill each one generously with the clam and cheese mixture. Be sure to pack them tightly for maximum flavor.
Place the stuffed mushrooms in a baking dish. Drizzle the remaining melted butter on top of the mushrooms. Sprinkle the additional mozzarella cheese over the stuffed caps for that gooey, cheesy finish. Bake in the preheated oven for about 20-25 minutes, or until the mushrooms are tender and the tops are golden brown.
Once they’re done baking, remove the stuffed mushrooms from the oven and let them cool for a few minutes. Serve them warm as a delightful appetizer or a side dish.
