Scoop avocado flesh in to a blender. Add the lemon juice, cream and blend. Blend in the chicken broth, cayenne and salt.
Divide among serving bowls and garnish with the garnish of your choice. Pass extra lemon, hot sauce etc so people can adjust to their taste.
This is best served immediately. You can hold it in the fridge an hour so by laying plastic wrap on the surface of the soup so no (or little) air can reach the avocado. If a gray film forms gently scrape it off before serving.