Cucumber soup

1. Heat oil in a large saucepan over medium-high heat. Add garlic and onion; cook, stirring occasionally, until tender, 1 to 4 minutes. Add lemon juice , and tarragon sauté  for 1 minute. Add cucumber slices, sauté for 1 minute add broth, salt, and pepper ; bring to a simmer. Reduce heat and cook at a gentle simmer until the cucumbers are soft, 6 to 8 minutes.
2. Transfer the soup to a blender. Add avocado and parsley; blend on low speed until smooth. (Use caution when pureeing hot liquids.) Pour into a serving bowl and stir in yogurt. Garnish was parsley, cilantro or chives. Serve the soup warm or refrigerate and serve it chilled.