Fry K&N's Croquettes as per instructions on label and set aside.
Melt margarine in a separate pan, add garlic and sauté for about half a minute.
Add black mushrooms, vinegar, yellow mustard, cream, chicken stock and basil, while stirring continuously.
Let simmer and add basil leaves to serve.
In a platter, arrange Croquettes and pour sauce over them to serve.