- Heat oil in a large saucepan over medium-high heat. Add garlic and onion. Cook, stirring occasionally, until tender. Add lemon juice and cook for 1 minute. Add cucumber slices, broth, salt, pepper and cayenne then bring to a simmer. Reduce heat and cook on low until the cucumbers are soft.
- Carefully transfer the soup to a blender. Add avocado and parsley; blend on low speed until smooth. Pour into a serving bowl and stir in yogurt. Serve warm or chilled. Just before serving, garnish with extra cucumber and chopped parsley.