Cut the avocados to half lengthwise and remove the seed. With the tip of a knife cut cubes on the inside of the avocado halves and with a spoon scoop the avocado out and mix it with the remaining ingredients. Pour the avocado-cucumber soup in an air tight plastic container, cover with a lid and refrigerate for at least 1 hour in order to blend flavors. Serve the avocado and cucumber soup cold in refrigerated soup bowls. Tip: You can substitute the buttermilk with natural Balkan yogurt mixed with iced water in proportion 1:1. The cold avocado and cucumber soup is a perfect starter for supper during the hot and muggy summer.