Step 1: Preheat the oven to 375°F (190°C). Line a baking sheet with parchment paper or foil for easier cleanup.
Step 2: Prepare the mushrooms by gently wiping them with a damp cloth or paper towel. Remove the stems and scoop out a little of the insides to create space for the filling.
Step 3: In a mixing bowl, combine the cooked seafood (crabmeat or shrimp), cream cheese, shredded Gouda cheese, Parmesan cheese, minced garlic, breadcrumbs (if using), lemon juice, and half of the chopped green onions. Season with salt and black pepper to taste. Mix until everything is well combined.
Step 4: Using a spoon, fill each mushroom cap generously with the seafood mixture. Arrange the stuffed mushrooms on the prepared baking sheet.
Step 5: Brush the tops of the stuffed mushrooms with melted butter to enhance flavor and help them brown during baking.
Step 6: Bake for about 20-25 minutes or until the mushrooms are tender, and the filling is golden and bubbly.
Step 7: Once baked, sprinkle the stuffed mushrooms with the remaining green onions and fresh parsley. Serve warm.