In a heavy-bottomed pot, sauté leek until softened and slightly browned. Remove one cup leek from pot; set aside. 

Add all remaining ingredients and bring to a boil. Lower heat and simmer for 30 minutes, or until vegetables are soft. 

Blend with an immersion blender; return sautéed leek to pot. Adjust seasoning to taste, and add a little more water to achieve desired consistency.