Preheat oven to 350ºF. Spray a baking sheet with cooking spray.

Clean mushrooms with a damp paper towel. Carefully break off stems. Chop stems extremely fine, discarding the tough ends of stems.

Heat oil in a large skillet over medium heat. Add garlic, minced stems, and minced onions. Fry until moisture has disappeared, taking care not to burn garlic. Set aside to cool.

When the garlic mixture is no longer hot, stir in cream cheese, parmesan cheese, black pepper, and cayenne pepper. Mixture should be very thick.

Using a little spoon, fill each mushroom cap with a generous amount of stuffing. Arrange the mushroom caps on the prepared cookie sheet.

Bake for 20 mins, or until the mushrooms are piping hot and liquid starts to form under caps.

Serve immediately for best taste.