Heat margarine and flour and make a roux.
Add vegetable broth gradually and bring to a boil. Do not pour all the vegetable broth at once and always stir well so that there are no lumps. Then add mustard and sour cream and bring to the boil again.
Add sugar to taste. It is best served with potatoes and boiled eggs. If you like a lot of sauce, the recipe is only enough for 2 – 3 servings.