Preheat oven to 180 degrees C. Line a baking tray with baking paper.
Clean mushrooms with a piece of damp kitchen paper. Carefully break off stems.
Chop stems finely - or puree in a blender - discarding any tough ends.
Brush mushroom cups with butter/margarine.
Heat oil in a large frying pan over medium heat (6-7).
Add garlic and chopped mushroom stems and gently cook until any moisture has disappeared, taking care not to burn garlic. Set aside to cool.
When garlic and mushroom mixture is cool, stir in cream cheese, parmesan cheese, black pepper and cayenne pepper. Mixture should be very thick. Using a teaspoon, fill each mushroom cap with a generous amount of stuffing.
Arrange the mushroom caps on prepared baking tray.
Bake for 20 minutes or until the mushrooms are piping hot and liquid starts to form under caps.
Can make up to 2 days in advance, cover well with cling wrap
(Could try in mini muffin tins or put some mixture on bottom of cups to hold still.)