Melt butter in a frying pan over medium heat.
Add onion. Cook, stirring, for 5 minutes or until softened.
Add garlic and mushrooms. Cook, stirring, for 3 to 4 minutes or until softened.
Add wine. Bring to the boil. Reduce heat to medium-low. Simmer for 2 to 3 minutes.
Stir in cream. Bring to the boil. Simmer for 10 minutes or until reduced by half.
Season with salt and pepper.