1 medium onion, peeled, halved and sliced thin

500g white closed cup mushrooms, trimmed and sliced thin (1 pound)

1 TBS tomato puree (tomato paste)

2 TBS plain flour (all purpose)

405ml of beef stock (1 3/4 cup)

60ml of ruby port or sherry

Put the potato flakes into a bowl.   Whisk in the milk.  Add the beef and salt and black pepper to taste.   Knead together until well combined.  Shape into 4 evenly sized patties which are 1/2 inch thick.  Place on a plate and cover.   Chill in the refrigerator for at least half an hour, or for up to four hours.

Melt 1 TBS of the butter in a large skillet over medium heat.   Add the beef patties and cook until well browned on each side, about 10 minutes in all.  Transfer to a plate and keep warm. 

Add the remaining butter to the skillet along with the sliced onion.   Cook until the onion is softened without browning, about 5 minutes or so.  Add the mushrooms and some seasoning.   Cook until any liquid has evaporated.  Stir in the tomato puree and the flour.  Cook until browned.   Slowly stir in the beef stock and the port.   Bring to a simmer.   Return the beef patties to the skillet, over and simmer over medium low heat for 12 to 15 minutes until cooked through and the flavours have melded well.   Taste and adjust gravy as desired.   Serve hot with plenty of mashed potatoes on the side.