Halve, pit, and peel avocados and in a blender or food processor blend with lemon or lime juice, broth, buttermilk, 2 cups ice water, cumin, Tabasco, and salt and pepper to taste until smooth. Transfer soup to a large bowl. Thin with remaining ice water to desired consistency and chill,
covered, until very cold, at least 2 hours and up to 4 (soup will discolor if kept longer.)
For the Chili Coriander Cream, in a blender or small food processor blend together all ingredients with salt and pepper to taste, scraping down sides until very smooth. Cream may be made 6 hours ahead and chilled.
Serve soup with Chili Coriander Cream and coriander sprigs.
Recipe courtesy of Gourmet Magazine