Brown ground sausage in a large skillet, over medium high heat, drain any oil, set aside.
Preheat oven to 350 degrees F (175 degrees C).
Spray a baking sheet with cooking spray.
Clean mushrooms by rubbing them down with a damp paper towel.
Carefully remove the stems, and cut off any tough ends. Discard any tough parts.
Chop stems extremely fine to use in the filling.
Remove sausage, from skillet, and place in a large mixing bowl, then in same skillet, heat olive oil over medium heat.
Add garlic, green onions, and chopped mushroom stems to the skillet.
Fry until any there isn’t a bunch of moisture left, but be careful not to burn the garlic.
Set aside to cool.
Once cooled, add to the bowl with the sausage, and stir in cream cheese, Parmesan cheese, black pepper, onion powder and cayenne pepper.
Mixture should be very thick. Use a spoon to spoon it into a zip top bag, then cut the corner off the bag to fill the mushroom caps.
Arrange the mushroom caps on prepared cookie sheet or mini muffin tin. Pipe filling into the cap.
Mix together panko and parmesan topping, and carefully roll each mushroom cap with filling in it so it is topped.
Spray top with cooking spray
Bake for 20 minutes in the preheated oven, or until the mushrooms are piping hot and liquid starts to form under caps.