Preheat your oven to 375°F (190°C). Gently wipe the mushrooms clean with a damp paper towel. Carefully remove the stems and finely chop them. Set the caps aside.

In a skillet over medium heat, melt 1 tbsp of butter. Add the chopped mushroom stems, minced garlic, and shallot. Cook for 5-7 minutes until soft and the moisture has evaporated. Let it cool slightly.

In a large bowl, combine the softened cream cheese, mayonnaise, Parmesan, and mozzarella. Add the crab meat, 1/3 cup of Panko, parsley, Old Bay, Worcestershire sauce, lemon juice, and black pepper. Gently fold in the cooked mushroom stem mixture.

Arrange the mushroom caps on a baking sheet or in a baking dish. Spoon the crab mixture evenly into each cap, mounding it slightly.

In a small bowl, mix the remaining 2 tbsp of Panko with 2 tbsp of melted butter. Sprinkle over the stuffed mushrooms. Bake for 20-25 minutes, until the topping is golden brown and the filling is bubbly.

Let cool for 5 minutes before serving. Garnish with extra fresh parsley if desired.