Heat the butter in a heavy-based frying pan.
Add the onion and garlic and sauté until onion is translucent.
Add the mushrooms and fry for 2 minutes.
Add the cake flour and mix through.
Heat the stock and sherry together and gradually add to the mushroom mixture.
Allow to simmer for 2 - 3 minutes or until mixture starts to thicken.
Add the cream and parsley and season to taste.