Preheat the oven to 400°F (200°C) and line a baking sheet with foil.
STEP 2
In a mixer, combine cream cheese, egg yolk, bread crumbs, green onion, lemon juice, Worcestershire sauce, garlic powder, salt, and pepper. Mix until smooth. Fold in crab and shrimp. Stuff the mushrooms with this mixture and top with remaining bread crumbs.
STEP 3
Place mushrooms on the baking sheet stuffing-side-up and bake for 12 to 14 minutes. Then, set the oven to broil for a few minutes until the tops are golden and bubbly.