Preheat your oven to 375°F. Gently rinse the mushroom caps and pat them completely dry with a paper towel. Lay them top down in a 9 by 13 inch casserole dish.

In a medium bowl, stir the softened cream cheese and egg yolk until completely smooth. Add the crumbled blue cheese, chopped green onion, bacon, minced garlic, salt, and pepper. Mix well to combine.

Spoon the filling evenly into each mushroom cap. Pack the filling firmly to prevent it from spilling out while baking.

Stir the blue cheese dressing and hot sauce together in a glass measuring cup. Drizzle this spicy sauce directly over the stuffed mushrooms.

Bake at 375°F for 20 minutes until the tops turn a golden brown. Let them cool for a few minutes before garnishing with extra green onion.