In medium saucepan over medium heat, melt butter. Add leeks.

Cook for about 5 minutes until leeks are tender.

Add potatoes and cook 5 minutes longer, stirring constantly.

Add chicken broth.

Over high heat continue cooking until soup is boiling.

Reduce heat to low. Cover and simmer for 15 minutes or until potatoes are tender.

In food processor or blender, puree 2/3rd of the soup.

Stir the puree into the rest of the soup.

Serve.

Add a dollop of sour cream and pumpkin seeds to garnish if desired.