Melt the butter in a pan and fry
all the vegetables until the fat has been absorbed. Add the stock and season with salt
and pepper. Bring to the boil and simmer for
about 45 minutes. Blend the flour with the milk and
stir it into the soup. Bring back to the boil and boil
for 2-3 minutes. Pour the soup into individual
bowls and sprinkle the cheese over the top.