Fry the onions in a frying pan with a tablespoon of oil and the Worcestershire sauce until soft and translucent then set aside in your casserole dish.
Mix the flour, salt and pepper, garlic salt and sage in a bowl and coat the meat a few pieces at a time.
Gently fry the meat on a medium heat with some more olive oil till brown on each side. Do not “crowd” the pan (I usually only do 5 or 6 pieces of meat at a time).
Add the browned meat to the onions in your casserole dish and give it a good stir to mix the meat and onions up.
When you have floured and browned all the meat you will have a little of the seasoned flour left over, put this to one side as you will need it later.
Put the fry pan back on the heat and add to it the glass of port then turn down the heat so the port does not boil.
Once the port is warm add the redcurrant jelly and the chocolate and continue to heat gently until both are melted.
Put the stock cube and the left over flour in a jug and add the boiling water stirring until you have a smooth paste, then add this to the port and heat gently stirring until you have a rich smooth sauce.
Add your sauce to the casserole dish and mix well then cover with a lid and place in the oven on the middle shelf for 20 minutes.
Remove and stir then return to the oven turning the temperature down to 160.
Cook for around 1 ½ hours or until the meat is tender.
If the gravy/sauce needs thickening put a spoonful of corn flour in a jug and add a few spoonful’s of the sauce stirring to a paste then add to the casserole mixing well return to the oven for a few minutes and give it another stir before serving.
Serve with steamed veg and your choice of potatoes or crusty bread.