Asparagus and Leek Soup

1. In a saucepan cook the leek (only white and pale green parts) and the garlic in the butter over moderately low heat, stirring, until the leek is softened. 2. Add the asparagus, the broth, and 1/2 cup water, and simmer the mixture, covered, for 10 to 12 minutes, or until the asparagus is very tender. 3. Puree 2/3 of the mixture in a blender until it is very smooth, stir the puree into the mixture remaining in the pan, and whisk in salt and pepper to taste. 4. Cook the soup over moderately low heat, but do not let it boil. 5. Note: also good to add 1/2 cup of sour cream or Greek yogurt after pureeing.