Wash leeks very carefully to remove all grit. Cut them horizontally and separate the rings to make sure no dirt remains. Coarsely chop them when washed.

In a medium soup pot, melt the butter and add the flour on low heat.

Using a wooden spoon, mix well. This will thicken your soup and give it a wonderful flavor.

Add chicken broth, leeks, onion, potatoes and bring to a boil.

Cover and simmer on low for about 20-25 minutes, until potatoes are soft.

Using an immersion blender, blend the soup until smooth adding the milk and adjusting salt and pepper to taste.

Serve immediately.