1. Cut the cucumbers in half lengthwise and scoop out the seeds with a spoon. If the cucumber is organic, leave the peel. If not, peel the cucumber. Chop coarsely and sprinkle with 1 teaspoon of salt. Set in a colander with a plate or bowl underneath and let drain. The salt helps remove additional liquid from the cucumbers. 
2. Place olive oil in a saucepan and heat on medium low flame. Add the shallots or onion and cook, stirring occasionally, until soft, about 5 minutes. Add stock and herbs.
3. Rinse the cucumbers quickly and add them to the soup. Cook over medium heat for 5 minutes. Turn off heat and let stand for about 10 minutes to cool slightly. 

4. Add avocado. Puree with soup in a blender or food processor, until smooth, being careful if soup is still hot. Taste and adjust seasoning.
5. Chill for several hours or overnight and serve.