Melt the
butter in a pan, add the onion and sauté over low heat for 10 minutes,
or until soft. Add the cabbage and cook for 5 minutes. Add the stock and
bay leaf. Bring to the boil, then reduce the heat, cover and simmer for
20 minutes. Season the soup with salt and pepper before spooning it into
serving bowls. Top with a spoonful of the sour cream and sprinkle with
the grated Parmesan. Serve with thick slices of fresh crusty bread.
