(civilian, non-fulminating version)
# 2oz butter
# 1oz plain flour
# half pint stock*
# 1 tablespoon vinegar
# 1 teaspoon ready mixed English mustard
# 1 tablespoon mushroom ketchup or port
# 1 tablespoon finely chopped parsley
# 6 pickled walnuts, diced
Melt the butter in the pan over a low heat then stir in the flour and cook gently for 2 to 3 minutes.
Add the stock gently, stirring all the while to prevent lumps forming.When the sauce is smooth and creamy add the vinegar, mustard and ketchup (or port).
Simmer the whole until it reaches a consistency that you like and then stir in the chopped parsley and walnuts.
Heat through for another minute or so and serve hot.