Fry 250g Onion or shallots in a frying pan with 4 tbsp olive oil over a high heat for about 3 mins until lightly browned, stirring often.
Season with ground black pepper and add 1 lightly crushed garlic clove and a sprig of rosemary. Cook for another 3 minutes stirring so it doesn't burn.

Pour in 5 tbsp balsamic vinegar and cook until evaporated away to a syrup, then pour in 400ml red wine and cook until reduced by two thirds Then Pour in 400ml beef or brown chicken stock and bring to the boil. Again let reduced by two thirds. Remove the Rosemary and Garlic.

Add the juices from the cooked meat (it alot then simmer until reduced again). Taste and Add Salt if needed.