Prepare the vegetables and cut them up small. Melt the butter in a large saucepan. Add the vegetables and sugar and cook them gently for 5–6 minutes. Stir in the stock and add the bouquet garni. Bring up to the boil, simmer for 2 minutes and then skim. Cover the pan with a lid and simmer gently for about 40–50 minutes or until the vegetables are quite tender.
Remove the bouquet garni an