Melt butter in a saucepan and add mushrooms and onion. Saute lightly.

Place mushrooms, onion and chicken stock into the slow cooker insert and stir well.

Cover with lid and cook on low for 5hrs.

30 minutes before serving, turn to high then stir in cream and milk.

Blend cornflour with 2 tblsp of the hot soup and blend until smooth. Stir flour mixture into the soup and cook until thickened.

Serve topped with parsley.