Perfect for a hot summer day, this bright and refreshing soup is sure to please. Lowfat buttermilk reduces the calorie count and adds a slight tang to the soup. If you can't find English cucumbers, remove the seeds from the common variety and proceed as directed.
Place the avocado, cucumber, scallions, garlic, salt, pepper, and cumin in the bowl of a food processor. Run the machine until the mixture is puréed, stopping and scraping down the sides of the bowl once or twice.
Add the lemon juice and 2 cups of the buttermilk to the food processor. Purée the mixture until smooth.
Add Tabasco to taste, and adjust salt and pepper as desired. Transfer to a clean bowl and refrigerate, covered, for at least 4 hours before serving. The soup will thicken a bit as it sits, so at serving time, add more buttermilk to adjust the consistency to your liking.