Melt butter in a large soup pot over medium-high heat. Add leeks and garlic and saute until tender, about 5 minutes. Add the soup, light cream, chicken broth and potatoes. Bring to a boil then reduce heat and let simmer for 15 minutes. Puree with a hand blender or in a blender, working in batches. (Soup can be stored in refrigerator for up to 2 days at this point.) Seasoning with salt and pepper. Serve hot garnished with chopped chives.