To make the gravy, fry the onions in the oil until starting to turn golden. Add the sugar and continue cooking, stirring frequently, until caramelised. Tip in the vinegar and allow to sizzle. Mix the flour with a couple of tbsp water. Pour the stock into the onions, then add the flour paste and cook, stirring constantly, until smooth and starting to thicken. When it is thick, pour into the tin with the faggots, cover with foil and bake for 1 hr until cooked through. Serve sprinkled with parsley, with mash and a veg, if you like.