Add the onion and garlic and stir well; then cover the pot. Let things cook for 10-15 mins, or until onion is transparent and soft.
Add the steamed broccoli and, using an immersion blender, liquefy the broccoli with the rest of the ingredients. You can also let the mixture cool and blend it in a regular blender, then reheat it before serving.
Add a dollop of cream to the soup when serving - this is optional but really tasty!