In the same pan as you cooked the sausages, fry the sliced onion in 1tbsp olive oil on a medium heat until softened. Add the sugar and a tbsp of water, and stir for a few mins until the sugar is dissolved. Add the wine if you are using. Add the stock and chutney, stir well, and turn up the heat so the mixture is bubbling. Let it bubble for a few minutes, until it starts to thicken, then turn down to medium heat.