Onion Gravy

Ingredients

25g/1 oz unsalted butter
1 medium onion sliced
1 tsp brown sugar
1 dessertspoon  plain flour
250 ml good quality vegetable stock (I like Marigold)
1/2 tsp balsamic vinegar (or more if liked)

Melt the butter in a medium pan and add the sliced onion and brown sugar.  Cook on a gentle heat until softened and beginning to caramelise.  (Cook to as dark as you dare if you want your gravy to have a good colour).  Add the flour to the mixture and stir for 1-2 mins. Very gradually add the stock to the cooked flour, stirring constantly.  Once the gravy starts to thicken stir in the balsamic vinegar and season to taste.  (You can sieve it or serve it with the onions in it.)
Freezes well.