Preheat oven to 375°F. Wash mushrooms. Removes stems from the mushrooms, mince and set aside. Place mushroom caps hole-side up in a baking pan
Cook the bacon in a medium skillet until it is crispy; remove bacon, crumble and set aside.
Add the garlic and minced mushroom stems to the bacon fat in the skillet. Cook 3 minutes or until the stems are cooked through. Stir in the cream cheese and cook until it is melted. Stir in the diced pecans and reserved bacon.
Fill mushrooms with a rounded spoonful of mixture.
Bake for 20 minutes or until the mushroom caps have cooked through. Sprinkle with green onion, if desired. Serve immediately.