Preheat your oven to 375°F (190°C).

Gently wipe each mushroom with a damp cloth and remove the stems. Finely chop the stems and set aside.

In a skillet, heat olive oil over medium heat. Add the chopped mushroom stems, onion, and garlic. Sauté for about 5 minutes.

Stir in shrimp and crab meat and cook for an additional 2-3 minutes.

Remove from heat and mix in cream cheese, Parmesan, mozzarella, parsley, lemon juice, salt, and pepper.

Stuff each mushroom cap with the seafood filling, packing it down lightly.

Arrange the stuffed mushrooms on a baking sheet and sprinkle with breadcrumbs if desired.

Bake for 15-20 minutes until the mushrooms are tender and the filling is bubbling.

Let cool slightly for about five minutes before serving warm.