Rinse the rice well in cold water - put it in a bowl or pot with some water and agitate it so that the water becomes cloudy. Drain then repeat. Drain again.
Wash the leek well and remove the outer layer and base. Cut the leek into medium slices.
Put the rice, leek and stock in a pot and bring to a simmer. Reduce the heat slightly and simmer around 10 minutes until the rice has cooked through. Season the broth to taste.
Put some chopped chicken in the bottom of each bowl and top with the soup, making sure each has a roughly equal amount of rice and leeks. Serve warm.
Notes
Instead of rice, you can use barley but it will take longer to cook (nearly double the time). You can top the soup with sliced prunes, if you like.